diff --git a/csharp/src/AddressBook/Addressbook.cs b/csharp/src/AddressBook/Addressbook.cs
index 379bf0a74254..d3e1ea95344f 100644
--- a/csharp/src/AddressBook/Addressbook.cs
+++ b/csharp/src/AddressBook/Addressbook.cs
@@ -49,7 +49,7 @@ public static partial class AddressbookReflection {
   /// <summary>
   /// [START messages]
   /// </summary>
-  public sealed partial class Person : pb::IMessage<Person>, pb::IMessage2 {
+  public sealed partial class Person : pb::IMessage<Person> {
     private static readonly pb::MessageParser<Person> _parser = new pb::MessageParser<Person>(() => new Person());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -289,13 +289,6 @@ public sealed partial class Person : pb::IMessage<Person>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!phones_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the Person message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -306,7 +299,7 @@ public enum PhoneType {
         [pbr::OriginalName("WORK")] Work = 2,
       }
 
-      public sealed partial class PhoneNumber : pb::IMessage<PhoneNumber>, pb::IMessage2 {
+      public sealed partial class PhoneNumber : pb::IMessage<PhoneNumber> {
         private static readonly pb::MessageParser<PhoneNumber> _parser = new pb::MessageParser<PhoneNumber>(() => new PhoneNumber());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -461,10 +454,6 @@ public sealed partial class PhoneNumber : pb::IMessage<PhoneNumber>, pb::IMessag
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -475,7 +464,7 @@ public sealed partial class PhoneNumber : pb::IMessage<PhoneNumber>, pb::IMessag
   /// <summary>
   /// Our address book file is just one of these.
   /// </summary>
-  public sealed partial class AddressBook : pb::IMessage<AddressBook>, pb::IMessage2 {
+  public sealed partial class AddressBook : pb::IMessage<AddressBook> {
     private static readonly pb::MessageParser<AddressBook> _parser = new pb::MessageParser<AddressBook>(() => new AddressBook());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -594,13 +583,6 @@ public sealed partial class AddressBook : pb::IMessage<AddressBook>, pb::IMessag
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!people_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf.Conformance/Conformance.cs b/csharp/src/Google.Protobuf.Conformance/Conformance.cs
index 3904d31d20cc..cd9b77abe5fc 100644
--- a/csharp/src/Google.Protobuf.Conformance/Conformance.cs
+++ b/csharp/src/Google.Protobuf.Conformance/Conformance.cs
@@ -86,7 +86,7 @@ public enum TestCategory {
   ///   2. parse the protobuf or JSON payload in "payload" (which may fail)
   ///   3. if the parse succeeded, serialize the message in the requested format.
   /// </summary>
-  public sealed partial class ConformanceRequest : pb::IMessage<ConformanceRequest>, pb::IMessage2 {
+  public sealed partial class ConformanceRequest : pb::IMessage<ConformanceRequest> {
     private static readonly pb::MessageParser<ConformanceRequest> _parser = new pb::MessageParser<ConformanceRequest>(() => new ConformanceRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -369,16 +369,12 @@ public enum PayloadOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Represents a single test case's output.
   /// </summary>
-  public sealed partial class ConformanceResponse : pb::IMessage<ConformanceResponse>, pb::IMessage2 {
+  public sealed partial class ConformanceResponse : pb::IMessage<ConformanceResponse> {
     private static readonly pb::MessageParser<ConformanceResponse> _parser = new pb::MessageParser<ConformanceResponse>(() => new ConformanceResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -717,10 +713,6 @@ public enum ResultOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/MapUnittestProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/MapUnittestProto3.cs
index 04f23d1e8ef2..6d3cd026d112 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/MapUnittestProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/MapUnittestProto3.cs
@@ -176,7 +176,7 @@ public enum MapEnum {
   /// <summary>
   /// Tests maps.
   /// </summary>
-  public sealed partial class TestMap : pb::IMessage<TestMap>, pb::IMessage2 {
+  public sealed partial class TestMap : pb::IMessage<TestMap> {
     private static readonly pb::MessageParser<TestMap> _parser = new pb::MessageParser<TestMap>(() => new TestMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -615,64 +615,9 @@ public sealed partial class TestMap : pb::IMessage<TestMap>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!mapInt32Int32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt64Int64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapUint32Uint32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapUint64Uint64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSint32Sint32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSint64Sint64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapFixed32Fixed32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapFixed64Fixed64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSfixed32Sfixed32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSfixed64Sfixed64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Float_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Double_.IsInitialized()) {
-        return false;
-      }
-      if (!mapBoolBool_.IsInitialized()) {
-        return false;
-      }
-      if (!mapStringString_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Bytes_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Enum_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32ForeignMessage_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  public sealed partial class TestMapSubmessage : pb::IMessage<TestMapSubmessage>, pb::IMessage2 {
+  public sealed partial class TestMapSubmessage : pb::IMessage<TestMapSubmessage> {
     private static readonly pb::MessageParser<TestMapSubmessage> _parser = new pb::MessageParser<TestMapSubmessage>(() => new TestMapSubmessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -805,13 +750,9 @@ public sealed partial class TestMapSubmessage : pb::IMessage<TestMapSubmessage>,
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestMessageMap : pb::IMessage<TestMessageMap>, pb::IMessage2 {
+  public sealed partial class TestMessageMap : pb::IMessage<TestMessageMap> {
     private static readonly pb::MessageParser<TestMessageMap> _parser = new pb::MessageParser<TestMessageMap>(() => new TestMessageMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -930,19 +871,12 @@ public sealed partial class TestMessageMap : pb::IMessage<TestMessageMap>, pb::I
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!mapInt32Message_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Two map fields share the same entry default instance.
   /// </summary>
-  public sealed partial class TestSameTypeMap : pb::IMessage<TestSameTypeMap>, pb::IMessage2 {
+  public sealed partial class TestSameTypeMap : pb::IMessage<TestSameTypeMap> {
     private static readonly pb::MessageParser<TestSameTypeMap> _parser = new pb::MessageParser<TestSameTypeMap>(() => new TestSameTypeMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1081,19 +1015,9 @@ public sealed partial class TestSameTypeMap : pb::IMessage<TestSameTypeMap>, pb:
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!map1_.IsInitialized()) {
-        return false;
-      }
-      if (!map2_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  public sealed partial class TestArenaMap : pb::IMessage<TestArenaMap>, pb::IMessage2 {
+  public sealed partial class TestArenaMap : pb::IMessage<TestArenaMap> {
     private static readonly pb::MessageParser<TestArenaMap> _parser = new pb::MessageParser<TestArenaMap>(() => new TestArenaMap());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1492,62 +1416,13 @@ public sealed partial class TestArenaMap : pb::IMessage<TestArenaMap>, pb::IMess
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!mapInt32Int32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt64Int64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapUint32Uint32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapUint64Uint64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSint32Sint32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSint64Sint64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapFixed32Fixed32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapFixed64Fixed64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSfixed32Sfixed32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSfixed64Sfixed64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Float_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Double_.IsInitialized()) {
-        return false;
-      }
-      if (!mapBoolBool_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Enum_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32ForeignMessage_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Previously, message containing enum called Type cannot be used as value of
   /// map field.
   /// </summary>
-  public sealed partial class MessageContainingEnumCalledType : pb::IMessage<MessageContainingEnumCalledType>, pb::IMessage2 {
+  public sealed partial class MessageContainingEnumCalledType : pb::IMessage<MessageContainingEnumCalledType> {
     private static readonly pb::MessageParser<MessageContainingEnumCalledType> _parser = new pb::MessageParser<MessageContainingEnumCalledType>(() => new MessageContainingEnumCalledType());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1666,13 +1541,6 @@ public sealed partial class MessageContainingEnumCalledType : pb::IMessage<Messa
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!type_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the MessageContainingEnumCalledType message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1689,7 +1557,7 @@ public enum Type {
   /// <summary>
   /// Previously, message cannot contain map field called "entry".
   /// </summary>
-  public sealed partial class MessageContainingMapCalledEntry : pb::IMessage<MessageContainingMapCalledEntry>, pb::IMessage2 {
+  public sealed partial class MessageContainingMapCalledEntry : pb::IMessage<MessageContainingMapCalledEntry> {
     private static readonly pb::MessageParser<MessageContainingMapCalledEntry> _parser = new pb::MessageParser<MessageContainingMapCalledEntry>(() => new MessageContainingMapCalledEntry());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1808,13 +1676,6 @@ public sealed partial class MessageContainingMapCalledEntry : pb::IMessage<Messa
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!entry_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/TestMessagesProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/TestMessagesProto3.cs
index d4670e186f21..d74422b59b32 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/TestMessagesProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/TestMessagesProto3.cs
@@ -233,7 +233,7 @@ public enum ForeignEnum {
   /// could trigger bugs that occur in any message type in this file.  We verify
   /// this stays true in a unit test.
   /// </summary>
-  public sealed partial class TestAllTypesProto3 : pb::IMessage<TestAllTypesProto3>, pb::IMessage2 {
+  public sealed partial class TestAllTypesProto3 : pb::IMessage<TestAllTypesProto3> {
     private static readonly pb::MessageParser<TestAllTypesProto3> _parser = new pb::MessageParser<TestAllTypesProto3>(() => new TestAllTypesProto3());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3424,118 +3424,6 @@ public enum OneofFieldOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!repeatedNestedMessage_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedForeignMessage_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Int32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt64Int64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapUint32Uint32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapUint64Uint64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSint32Sint32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSint64Sint64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapFixed32Fixed32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapFixed64Fixed64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSfixed32Sfixed32_.IsInitialized()) {
-        return false;
-      }
-      if (!mapSfixed64Sfixed64_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Float_.IsInitialized()) {
-        return false;
-      }
-      if (!mapInt32Double_.IsInitialized()) {
-        return false;
-      }
-      if (!mapBoolBool_.IsInitialized()) {
-        return false;
-      }
-      if (!mapStringString_.IsInitialized()) {
-        return false;
-      }
-      if (!mapStringBytes_.IsInitialized()) {
-        return false;
-      }
-      if (!mapStringNestedMessage_.IsInitialized()) {
-        return false;
-      }
-      if (!mapStringForeignMessage_.IsInitialized()) {
-        return false;
-      }
-      if (!mapStringNestedEnum_.IsInitialized()) {
-        return false;
-      }
-      if (!mapStringForeignEnum_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedBoolWrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedInt32Wrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedInt64Wrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedUint32Wrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedUint64Wrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedFloatWrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedDoubleWrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedStringWrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedBytesWrapper_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedDuration_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedTimestamp_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedFieldmask_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedAny_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedValue_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedStruct_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the TestAllTypesProto3 message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3550,7 +3438,7 @@ public enum NestedEnum {
         [pbr::OriginalName("NEG")] Neg = -1,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMessage2 {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage> {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3711,10 +3599,6 @@ public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMe
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -3722,7 +3606,7 @@ public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMe
 
   }
 
-  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>, pb::IMessage2 {
+  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage> {
     private static readonly pb::MessageParser<ForeignMessage> _parser = new pb::MessageParser<ForeignMessage>(() => new ForeignMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3849,10 +3733,6 @@ public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>, pb::I
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestCustomOptionsProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestCustomOptionsProto3.cs
index 4dbe849b2d1b..2a9efe55fff1 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestCustomOptionsProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestCustomOptionsProto3.cs
@@ -183,7 +183,7 @@ public enum AggregateEnum {
   /// A test message with custom options at all possible locations (and also some
   /// regular options, to make sure they interact nicely).
   /// </summary>
-  public sealed partial class TestMessageWithCustomOptions : pb::IMessage<TestMessageWithCustomOptions>, pb::IMessage2 {
+  public sealed partial class TestMessageWithCustomOptions : pb::IMessage<TestMessageWithCustomOptions> {
     private static readonly pb::MessageParser<TestMessageWithCustomOptions> _parser = new pb::MessageParser<TestMessageWithCustomOptions>(() => new TestMessageWithCustomOptions());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -366,10 +366,6 @@ public enum AnOneofOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the TestMessageWithCustomOptions message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -389,7 +385,7 @@ public enum AnEnum {
   /// A test RPC service with custom options at all possible locations (and also
   /// some regular options, to make sure they interact nicely).
   /// </summary>
-  public sealed partial class CustomOptionFooRequest : pb::IMessage<CustomOptionFooRequest>, pb::IMessage2 {
+  public sealed partial class CustomOptionFooRequest : pb::IMessage<CustomOptionFooRequest> {
     private static readonly pb::MessageParser<CustomOptionFooRequest> _parser = new pb::MessageParser<CustomOptionFooRequest>(() => new CustomOptionFooRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -488,13 +484,9 @@ public sealed partial class CustomOptionFooRequest : pb::IMessage<CustomOptionFo
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class CustomOptionFooResponse : pb::IMessage<CustomOptionFooResponse>, pb::IMessage2 {
+  public sealed partial class CustomOptionFooResponse : pb::IMessage<CustomOptionFooResponse> {
     private static readonly pb::MessageParser<CustomOptionFooResponse> _parser = new pb::MessageParser<CustomOptionFooResponse>(() => new CustomOptionFooResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -593,13 +585,9 @@ public sealed partial class CustomOptionFooResponse : pb::IMessage<CustomOptionF
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class CustomOptionFooClientMessage : pb::IMessage<CustomOptionFooClientMessage>, pb::IMessage2 {
+  public sealed partial class CustomOptionFooClientMessage : pb::IMessage<CustomOptionFooClientMessage> {
     private static readonly pb::MessageParser<CustomOptionFooClientMessage> _parser = new pb::MessageParser<CustomOptionFooClientMessage>(() => new CustomOptionFooClientMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -698,13 +686,9 @@ public sealed partial class CustomOptionFooClientMessage : pb::IMessage<CustomOp
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class CustomOptionFooServerMessage : pb::IMessage<CustomOptionFooServerMessage>, pb::IMessage2 {
+  public sealed partial class CustomOptionFooServerMessage : pb::IMessage<CustomOptionFooServerMessage> {
     private static readonly pb::MessageParser<CustomOptionFooServerMessage> _parser = new pb::MessageParser<CustomOptionFooServerMessage>(() => new CustomOptionFooServerMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -803,13 +787,9 @@ public sealed partial class CustomOptionFooServerMessage : pb::IMessage<CustomOp
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class DummyMessageContainingEnum : pb::IMessage<DummyMessageContainingEnum>, pb::IMessage2 {
+  public sealed partial class DummyMessageContainingEnum : pb::IMessage<DummyMessageContainingEnum> {
     private static readonly pb::MessageParser<DummyMessageContainingEnum> _parser = new pb::MessageParser<DummyMessageContainingEnum>(() => new DummyMessageContainingEnum());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -908,10 +888,6 @@ public sealed partial class DummyMessageContainingEnum : pb::IMessage<DummyMessa
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the DummyMessageContainingEnum message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -927,7 +903,7 @@ public enum TestEnumType {
 
   }
 
-  public sealed partial class DummyMessageInvalidAsOptionType : pb::IMessage<DummyMessageInvalidAsOptionType>, pb::IMessage2 {
+  public sealed partial class DummyMessageInvalidAsOptionType : pb::IMessage<DummyMessageInvalidAsOptionType> {
     private static readonly pb::MessageParser<DummyMessageInvalidAsOptionType> _parser = new pb::MessageParser<DummyMessageInvalidAsOptionType>(() => new DummyMessageInvalidAsOptionType());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1026,13 +1002,9 @@ public sealed partial class DummyMessageInvalidAsOptionType : pb::IMessage<Dummy
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class CustomOptionMinIntegerValues : pb::IMessage<CustomOptionMinIntegerValues>, pb::IMessage2 {
+  public sealed partial class CustomOptionMinIntegerValues : pb::IMessage<CustomOptionMinIntegerValues> {
     private static readonly pb::MessageParser<CustomOptionMinIntegerValues> _parser = new pb::MessageParser<CustomOptionMinIntegerValues>(() => new CustomOptionMinIntegerValues());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1131,13 +1103,9 @@ public sealed partial class CustomOptionMinIntegerValues : pb::IMessage<CustomOp
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class CustomOptionMaxIntegerValues : pb::IMessage<CustomOptionMaxIntegerValues>, pb::IMessage2 {
+  public sealed partial class CustomOptionMaxIntegerValues : pb::IMessage<CustomOptionMaxIntegerValues> {
     private static readonly pb::MessageParser<CustomOptionMaxIntegerValues> _parser = new pb::MessageParser<CustomOptionMaxIntegerValues>(() => new CustomOptionMaxIntegerValues());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1236,13 +1204,9 @@ public sealed partial class CustomOptionMaxIntegerValues : pb::IMessage<CustomOp
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class CustomOptionOtherValues : pb::IMessage<CustomOptionOtherValues>, pb::IMessage2 {
+  public sealed partial class CustomOptionOtherValues : pb::IMessage<CustomOptionOtherValues> {
     private static readonly pb::MessageParser<CustomOptionOtherValues> _parser = new pb::MessageParser<CustomOptionOtherValues>(() => new CustomOptionOtherValues());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1341,13 +1305,9 @@ public sealed partial class CustomOptionOtherValues : pb::IMessage<CustomOptionO
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class SettingRealsFromPositiveInts : pb::IMessage<SettingRealsFromPositiveInts>, pb::IMessage2 {
+  public sealed partial class SettingRealsFromPositiveInts : pb::IMessage<SettingRealsFromPositiveInts> {
     private static readonly pb::MessageParser<SettingRealsFromPositiveInts> _parser = new pb::MessageParser<SettingRealsFromPositiveInts>(() => new SettingRealsFromPositiveInts());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1446,13 +1406,9 @@ public sealed partial class SettingRealsFromPositiveInts : pb::IMessage<SettingR
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class SettingRealsFromNegativeInts : pb::IMessage<SettingRealsFromNegativeInts>, pb::IMessage2 {
+  public sealed partial class SettingRealsFromNegativeInts : pb::IMessage<SettingRealsFromNegativeInts> {
     private static readonly pb::MessageParser<SettingRealsFromNegativeInts> _parser = new pb::MessageParser<SettingRealsFromNegativeInts>(() => new SettingRealsFromNegativeInts());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1551,13 +1507,9 @@ public sealed partial class SettingRealsFromNegativeInts : pb::IMessage<SettingR
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class ComplexOptionType1 : pb::IMessage<ComplexOptionType1>, pb::IMessage2 {
+  public sealed partial class ComplexOptionType1 : pb::IMessage<ComplexOptionType1> {
     private static readonly pb::MessageParser<ComplexOptionType1> _parser = new pb::MessageParser<ComplexOptionType1>(() => new ComplexOptionType1());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1761,13 +1713,9 @@ public sealed partial class ComplexOptionType1 : pb::IMessage<ComplexOptionType1
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class ComplexOptionType2 : pb::IMessage<ComplexOptionType2>, pb::IMessage2 {
+  public sealed partial class ComplexOptionType2 : pb::IMessage<ComplexOptionType2> {
     private static readonly pb::MessageParser<ComplexOptionType2> _parser = new pb::MessageParser<ComplexOptionType2>(() => new ComplexOptionType2());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1982,18 +1930,11 @@ public sealed partial class ComplexOptionType2 : pb::IMessage<ComplexOptionType2
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!barney_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the ComplexOptionType2 message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class ComplexOptionType4 : pb::IMessage<ComplexOptionType4>, pb::IMessage2 {
+      public sealed partial class ComplexOptionType4 : pb::IMessage<ComplexOptionType4> {
         private static readonly pb::MessageParser<ComplexOptionType4> _parser = new pb::MessageParser<ComplexOptionType4>(() => new ComplexOptionType4());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2120,10 +2061,6 @@ public sealed partial class ComplexOptionType4 : pb::IMessage<ComplexOptionType4
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -2131,7 +2068,7 @@ public sealed partial class ComplexOptionType4 : pb::IMessage<ComplexOptionType4
 
   }
 
-  public sealed partial class ComplexOptionType3 : pb::IMessage<ComplexOptionType3>, pb::IMessage2 {
+  public sealed partial class ComplexOptionType3 : pb::IMessage<ComplexOptionType3> {
     private static readonly pb::MessageParser<ComplexOptionType3> _parser = new pb::MessageParser<ComplexOptionType3>(() => new ComplexOptionType3());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2258,16 +2195,12 @@ public sealed partial class ComplexOptionType3 : pb::IMessage<ComplexOptionType3
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Note that we try various different ways of naming the same extension.
   /// </summary>
-  public sealed partial class VariousComplexOptions : pb::IMessage<VariousComplexOptions>, pb::IMessage2 {
+  public sealed partial class VariousComplexOptions : pb::IMessage<VariousComplexOptions> {
     private static readonly pb::MessageParser<VariousComplexOptions> _parser = new pb::MessageParser<VariousComplexOptions>(() => new VariousComplexOptions());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2366,16 +2299,12 @@ public sealed partial class VariousComplexOptions : pb::IMessage<VariousComplexO
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// A helper type used to test aggregate option parsing
   /// </summary>
-  public sealed partial class Aggregate : pb::IMessage<Aggregate>, pb::IMessage2 {
+  public sealed partial class Aggregate : pb::IMessage<Aggregate> {
     private static readonly pb::MessageParser<Aggregate> _parser = new pb::MessageParser<Aggregate>(() => new Aggregate());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2567,13 +2496,9 @@ public sealed partial class Aggregate : pb::IMessage<Aggregate>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class AggregateMessage : pb::IMessage<AggregateMessage>, pb::IMessage2 {
+  public sealed partial class AggregateMessage : pb::IMessage<AggregateMessage> {
     private static readonly pb::MessageParser<AggregateMessage> _parser = new pb::MessageParser<AggregateMessage>(() => new AggregateMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2700,16 +2625,12 @@ public sealed partial class AggregateMessage : pb::IMessage<AggregateMessage>, p
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test custom options for nested type.
   /// </summary>
-  public sealed partial class NestedOptionType : pb::IMessage<NestedOptionType>, pb::IMessage2 {
+  public sealed partial class NestedOptionType : pb::IMessage<NestedOptionType> {
     private static readonly pb::MessageParser<NestedOptionType> _parser = new pb::MessageParser<NestedOptionType>(() => new NestedOptionType());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2808,10 +2729,6 @@ public sealed partial class NestedOptionType : pb::IMessage<NestedOptionType>, p
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the NestedOptionType message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2821,7 +2738,7 @@ public enum NestedEnum {
         [pbr::OriginalName("NESTED_ENUM_VALUE")] Value = 1,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMessage2 {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage> {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2948,10 +2865,6 @@ public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMe
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportProto3.cs
index ebbc30295593..6bf97151715e 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportProto3.cs
@@ -50,7 +50,7 @@ public enum ImportEnum {
   #endregion
 
   #region Messages
-  public sealed partial class ImportMessage : pb::IMessage<ImportMessage>, pb::IMessage2 {
+  public sealed partial class ImportMessage : pb::IMessage<ImportMessage> {
     private static readonly pb::MessageParser<ImportMessage> _parser = new pb::MessageParser<ImportMessage>(() => new ImportMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -177,10 +177,6 @@ public sealed partial class ImportMessage : pb::IMessage<ImportMessage>, pb::IMe
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportPublicProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportPublicProto3.cs
index e14c5dd07ee4..97d181aff48c 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportPublicProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestImportPublicProto3.cs
@@ -38,7 +38,7 @@ public static partial class UnittestImportPublicProto3Reflection {
 
   }
   #region Messages
-  public sealed partial class PublicImportMessage : pb::IMessage<PublicImportMessage>, pb::IMessage2 {
+  public sealed partial class PublicImportMessage : pb::IMessage<PublicImportMessage> {
     private static readonly pb::MessageParser<PublicImportMessage> _parser = new pb::MessageParser<PublicImportMessage>(() => new PublicImportMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -165,10 +165,6 @@ public sealed partial class PublicImportMessage : pb::IMessage<PublicImportMessa
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestIssues.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestIssues.cs
index 2997994a0f36..f27ab6407497 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestIssues.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestIssues.cs
@@ -88,7 +88,7 @@ public enum DeprecatedEnum {
   /// Issue 307: when generating doubly-nested types, any references
   /// should be of the form A.Types.B.Types.C.
   /// </summary>
-  public sealed partial class Issue307 : pb::IMessage<Issue307>, pb::IMessage2 {
+  public sealed partial class Issue307 : pb::IMessage<Issue307> {
     private static readonly pb::MessageParser<Issue307> _parser = new pb::MessageParser<Issue307>(() => new Issue307());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -187,15 +187,11 @@ public sealed partial class Issue307 : pb::IMessage<Issue307>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the Issue307 message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class NestedOnce : pb::IMessage<NestedOnce>, pb::IMessage2 {
+      public sealed partial class NestedOnce : pb::IMessage<NestedOnce> {
         private static readonly pb::MessageParser<NestedOnce> _parser = new pb::MessageParser<NestedOnce>(() => new NestedOnce());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -294,15 +290,11 @@ public sealed partial class NestedOnce : pb::IMessage<NestedOnce>, pb::IMessage2
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
         #region Nested types
         /// <summary>Container for nested types declared in the NestedOnce message type.</summary>
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
         public static partial class Types {
-          public sealed partial class NestedTwice : pb::IMessage<NestedTwice>, pb::IMessage2 {
+          public sealed partial class NestedTwice : pb::IMessage<NestedTwice> {
             private static readonly pb::MessageParser<NestedTwice> _parser = new pb::MessageParser<NestedTwice>(() => new NestedTwice());
             private pb::UnknownFieldSet _unknownFields;
             [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -401,10 +393,6 @@ public sealed partial class NestedTwice : pb::IMessage<NestedTwice>, pb::IMessag
               }
             }
 
-            [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-            public bool IsInitialized() {
-              return true;
-            }
           }
 
         }
@@ -417,7 +405,7 @@ public sealed partial class NestedTwice : pb::IMessage<NestedTwice>, pb::IMessag
 
   }
 
-  public sealed partial class NegativeEnumMessage : pb::IMessage<NegativeEnumMessage>, pb::IMessage2 {
+  public sealed partial class NegativeEnumMessage : pb::IMessage<NegativeEnumMessage> {
     private static readonly pb::MessageParser<NegativeEnumMessage> _parser = new pb::MessageParser<NegativeEnumMessage>(() => new NegativeEnumMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -586,13 +574,9 @@ public sealed partial class NegativeEnumMessage : pb::IMessage<NegativeEnumMessa
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class DeprecatedChild : pb::IMessage<DeprecatedChild>, pb::IMessage2 {
+  public sealed partial class DeprecatedChild : pb::IMessage<DeprecatedChild> {
     private static readonly pb::MessageParser<DeprecatedChild> _parser = new pb::MessageParser<DeprecatedChild>(() => new DeprecatedChild());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -691,13 +675,9 @@ public sealed partial class DeprecatedChild : pb::IMessage<DeprecatedChild>, pb:
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class DeprecatedFieldsMessage : pb::IMessage<DeprecatedFieldsMessage>, pb::IMessage2 {
+  public sealed partial class DeprecatedFieldsMessage : pb::IMessage<DeprecatedFieldsMessage> {
     private static readonly pb::MessageParser<DeprecatedFieldsMessage> _parser = new pb::MessageParser<DeprecatedFieldsMessage>(() => new DeprecatedFieldsMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -954,19 +934,12 @@ public sealed partial class DeprecatedFieldsMessage : pb::IMessage<DeprecatedFie
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!messageArray_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Issue 45: http://code.google.com/p/protobuf-csharp-port/issues/detail?id=45
   /// </summary>
-  public sealed partial class ItemField : pb::IMessage<ItemField>, pb::IMessage2 {
+  public sealed partial class ItemField : pb::IMessage<ItemField> {
     private static readonly pb::MessageParser<ItemField> _parser = new pb::MessageParser<ItemField>(() => new ItemField());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1093,13 +1066,9 @@ public sealed partial class ItemField : pb::IMessage<ItemField>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class ReservedNames : pb::IMessage<ReservedNames>, pb::IMessage2 {
+  public sealed partial class ReservedNames : pb::IMessage<ReservedNames> {
     private static readonly pb::MessageParser<ReservedNames> _parser = new pb::MessageParser<ReservedNames>(() => new ReservedNames());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1254,10 +1223,6 @@ public sealed partial class ReservedNames : pb::IMessage<ReservedNames>, pb::IMe
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the ReservedNames message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1265,7 +1230,7 @@ public static partial class Types {
       /// <summary>
       /// Force a nested type called Types
       /// </summary>
-      public sealed partial class SomeNestedType : pb::IMessage<SomeNestedType>, pb::IMessage2 {
+      public sealed partial class SomeNestedType : pb::IMessage<SomeNestedType> {
         private static readonly pb::MessageParser<SomeNestedType> _parser = new pb::MessageParser<SomeNestedType>(() => new SomeNestedType());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1364,10 +1329,6 @@ public sealed partial class SomeNestedType : pb::IMessage<SomeNestedType>, pb::I
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -1387,7 +1348,7 @@ public sealed partial class SomeNestedType : pb::IMessage<SomeNestedType>, pb::I
   /// Alternatively, consider just adding this to
   /// unittest_proto3.proto if multiple platforms want it.
   /// </summary>
-  public sealed partial class TestJsonFieldOrdering : pb::IMessage<TestJsonFieldOrdering>, pb::IMessage2 {
+  public sealed partial class TestJsonFieldOrdering : pb::IMessage<TestJsonFieldOrdering> {
     private static readonly pb::MessageParser<TestJsonFieldOrdering> _parser = new pb::MessageParser<TestJsonFieldOrdering>(() => new TestJsonFieldOrdering());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1716,13 +1677,9 @@ public enum O2OneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestJsonName : pb::IMessage<TestJsonName>, pb::IMessage2 {
+  public sealed partial class TestJsonName : pb::IMessage<TestJsonName> {
     private static readonly pb::MessageParser<TestJsonName> _parser = new pb::MessageParser<TestJsonName>(() => new TestJsonName());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1908,10 +1865,6 @@ public sealed partial class TestJsonName : pb::IMessage<TestJsonName>, pb::IMess
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -1919,7 +1872,7 @@ public sealed partial class TestJsonName : pb::IMessage<TestJsonName>, pb::IMess
   /// oneof case, which is itself a message type, the submessages should
   /// be merged.
   /// </summary>
-  public sealed partial class OneofMerging : pb::IMessage<OneofMerging>, pb::IMessage2 {
+  public sealed partial class OneofMerging : pb::IMessage<OneofMerging> {
     private static readonly pb::MessageParser<OneofMerging> _parser = new pb::MessageParser<OneofMerging>(() => new OneofMerging());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2113,15 +2066,11 @@ public enum ValueOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the OneofMerging message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class Nested : pb::IMessage<Nested>, pb::IMessage2 {
+      public sealed partial class Nested : pb::IMessage<Nested> {
         private static readonly pb::MessageParser<Nested> _parser = new pb::MessageParser<Nested>(() => new Nested());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2276,10 +2225,6 @@ public sealed partial class Nested : pb::IMessage<Nested>, pb::IMessage2 {
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestProto3.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestProto3.cs
index 70ded9bc8f83..4efeab8741b5 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestProto3.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestProto3.cs
@@ -240,7 +240,7 @@ public enum TestSparseEnum {
   /// This proto includes every type of field in both singular and repeated
   /// forms.
   /// </summary>
-  public sealed partial class TestAllTypes : pb::IMessage<TestAllTypes>, pb::IMessage2 {
+  public sealed partial class TestAllTypes : pb::IMessage<TestAllTypes> {
     private static readonly pb::MessageParser<TestAllTypes> _parser = new pb::MessageParser<TestAllTypes>(() => new TestAllTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1604,22 +1604,6 @@ public enum OneofFieldOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!repeatedNestedMessage_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedForeignMessage_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedImportMessage_.IsInitialized()) {
-        return false;
-      }
-      if (!repeatedPublicImportMessage_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the TestAllTypes message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1635,7 +1619,7 @@ public enum NestedEnum {
         [pbr::OriginalName("NEG")] Neg = -1,
       }
 
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMessage2 {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage> {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1767,10 +1751,6 @@ public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMe
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -1781,7 +1761,7 @@ public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMe
   /// <summary>
   /// This proto includes a recusively nested message.
   /// </summary>
-  public sealed partial class NestedTestAllTypes : pb::IMessage<NestedTestAllTypes>, pb::IMessage2 {
+  public sealed partial class NestedTestAllTypes : pb::IMessage<NestedTestAllTypes> {
     private static readonly pb::MessageParser<NestedTestAllTypes> _parser = new pb::MessageParser<NestedTestAllTypes>(() => new NestedTestAllTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1968,16 +1948,9 @@ public sealed partial class NestedTestAllTypes : pb::IMessage<NestedTestAllTypes
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!repeatedChild_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  public sealed partial class TestDeprecatedFields : pb::IMessage<TestDeprecatedFields>, pb::IMessage2 {
+  public sealed partial class TestDeprecatedFields : pb::IMessage<TestDeprecatedFields> {
     private static readonly pb::MessageParser<TestDeprecatedFields> _parser = new pb::MessageParser<TestDeprecatedFields>(() => new TestDeprecatedFields());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2105,17 +2078,13 @@ public sealed partial class TestDeprecatedFields : pb::IMessage<TestDeprecatedFi
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Define these after TestAllTypes to make sure the compiler can handle
   /// that.
   /// </summary>
-  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>, pb::IMessage2 {
+  public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage> {
     private static readonly pb::MessageParser<ForeignMessage> _parser = new pb::MessageParser<ForeignMessage>(() => new ForeignMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2242,13 +2211,9 @@ public sealed partial class ForeignMessage : pb::IMessage<ForeignMessage>, pb::I
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestReservedFields : pb::IMessage<TestReservedFields>, pb::IMessage2 {
+  public sealed partial class TestReservedFields : pb::IMessage<TestReservedFields> {
     private static readonly pb::MessageParser<TestReservedFields> _parser = new pb::MessageParser<TestReservedFields>(() => new TestReservedFields());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2347,16 +2312,12 @@ public sealed partial class TestReservedFields : pb::IMessage<TestReservedFields
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test that we can use NestedMessage from outside TestAllTypes.
   /// </summary>
-  public sealed partial class TestForeignNested : pb::IMessage<TestForeignNested>, pb::IMessage2 {
+  public sealed partial class TestForeignNested : pb::IMessage<TestForeignNested> {
     private static readonly pb::MessageParser<TestForeignNested> _parser = new pb::MessageParser<TestForeignNested>(() => new TestForeignNested());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2489,16 +2450,12 @@ public sealed partial class TestForeignNested : pb::IMessage<TestForeignNested>,
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test that really large tag numbers don't break anything.
   /// </summary>
-  public sealed partial class TestReallyLargeTagNumber : pb::IMessage<TestReallyLargeTagNumber>, pb::IMessage2 {
+  public sealed partial class TestReallyLargeTagNumber : pb::IMessage<TestReallyLargeTagNumber> {
     private static readonly pb::MessageParser<TestReallyLargeTagNumber> _parser = new pb::MessageParser<TestReallyLargeTagNumber>(() => new TestReallyLargeTagNumber());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2657,13 +2614,9 @@ public sealed partial class TestReallyLargeTagNumber : pb::IMessage<TestReallyLa
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestRecursiveMessage : pb::IMessage<TestRecursiveMessage>, pb::IMessage2 {
+  public sealed partial class TestRecursiveMessage : pb::IMessage<TestRecursiveMessage> {
     private static readonly pb::MessageParser<TestRecursiveMessage> _parser = new pb::MessageParser<TestRecursiveMessage>(() => new TestRecursiveMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2824,16 +2777,12 @@ public sealed partial class TestRecursiveMessage : pb::IMessage<TestRecursiveMes
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test that mutual recursion works.
   /// </summary>
-  public sealed partial class TestMutualRecursionA : pb::IMessage<TestMutualRecursionA>, pb::IMessage2 {
+  public sealed partial class TestMutualRecursionA : pb::IMessage<TestMutualRecursionA> {
     private static readonly pb::MessageParser<TestMutualRecursionA> _parser = new pb::MessageParser<TestMutualRecursionA>(() => new TestMutualRecursionA());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2966,13 +2915,9 @@ public sealed partial class TestMutualRecursionA : pb::IMessage<TestMutualRecurs
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestMutualRecursionB : pb::IMessage<TestMutualRecursionB>, pb::IMessage2 {
+  public sealed partial class TestMutualRecursionB : pb::IMessage<TestMutualRecursionB> {
     private static readonly pb::MessageParser<TestMutualRecursionB> _parser = new pb::MessageParser<TestMutualRecursionB>(() => new TestMutualRecursionB());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3133,13 +3078,9 @@ public sealed partial class TestMutualRecursionB : pb::IMessage<TestMutualRecurs
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestEnumAllowAlias : pb::IMessage<TestEnumAllowAlias>, pb::IMessage2 {
+  public sealed partial class TestEnumAllowAlias : pb::IMessage<TestEnumAllowAlias> {
     private static readonly pb::MessageParser<TestEnumAllowAlias> _parser = new pb::MessageParser<TestEnumAllowAlias>(() => new TestEnumAllowAlias());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3266,17 +3207,13 @@ public sealed partial class TestEnumAllowAlias : pb::IMessage<TestEnumAllowAlias
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test message with CamelCase field names.  This violates Protocol Buffer
   /// standard style.
   /// </summary>
-  public sealed partial class TestCamelCaseFieldNames : pb::IMessage<TestCamelCaseFieldNames>, pb::IMessage2 {
+  public sealed partial class TestCamelCaseFieldNames : pb::IMessage<TestCamelCaseFieldNames> {
     private static readonly pb::MessageParser<TestCamelCaseFieldNames> _parser = new pb::MessageParser<TestCamelCaseFieldNames>(() => new TestCamelCaseFieldNames());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3575,20 +3512,13 @@ public sealed partial class TestCamelCaseFieldNames : pb::IMessage<TestCamelCase
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!repeatedMessageField_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// We list fields out of order, to ensure that we're using field number and not
   /// field index to determine serialization order.
   /// </summary>
-  public sealed partial class TestFieldOrderings : pb::IMessage<TestFieldOrderings>, pb::IMessage2 {
+  public sealed partial class TestFieldOrderings : pb::IMessage<TestFieldOrderings> {
     private static readonly pb::MessageParser<TestFieldOrderings> _parser = new pb::MessageParser<TestFieldOrderings>(() => new TestFieldOrderings());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3805,15 +3735,11 @@ public sealed partial class TestFieldOrderings : pb::IMessage<TestFieldOrderings
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the TestFieldOrderings message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMessage2 {
+      public sealed partial class NestedMessage : pb::IMessage<NestedMessage> {
         private static readonly pb::MessageParser<NestedMessage> _parser = new pb::MessageParser<NestedMessage>(() => new NestedMessage());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3973,10 +3899,6 @@ public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMe
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -3984,7 +3906,7 @@ public sealed partial class NestedMessage : pb::IMessage<NestedMessage>, pb::IMe
 
   }
 
-  public sealed partial class SparseEnumMessage : pb::IMessage<SparseEnumMessage>, pb::IMessage2 {
+  public sealed partial class SparseEnumMessage : pb::IMessage<SparseEnumMessage> {
     private static readonly pb::MessageParser<SparseEnumMessage> _parser = new pb::MessageParser<SparseEnumMessage>(() => new SparseEnumMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4111,16 +4033,12 @@ public sealed partial class SparseEnumMessage : pb::IMessage<SparseEnumMessage>,
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test String and Bytes: string is for valid UTF-8 strings
   /// </summary>
-  public sealed partial class OneString : pb::IMessage<OneString>, pb::IMessage2 {
+  public sealed partial class OneString : pb::IMessage<OneString> {
     private static readonly pb::MessageParser<OneString> _parser = new pb::MessageParser<OneString>(() => new OneString());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4247,13 +4165,9 @@ public sealed partial class OneString : pb::IMessage<OneString>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class MoreString : pb::IMessage<MoreString>, pb::IMessage2 {
+  public sealed partial class MoreString : pb::IMessage<MoreString> {
     private static readonly pb::MessageParser<MoreString> _parser = new pb::MessageParser<MoreString>(() => new MoreString());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4372,13 +4286,9 @@ public sealed partial class MoreString : pb::IMessage<MoreString>, pb::IMessage2
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class OneBytes : pb::IMessage<OneBytes>, pb::IMessage2 {
+  public sealed partial class OneBytes : pb::IMessage<OneBytes> {
     private static readonly pb::MessageParser<OneBytes> _parser = new pb::MessageParser<OneBytes>(() => new OneBytes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4505,13 +4415,9 @@ public sealed partial class OneBytes : pb::IMessage<OneBytes>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class MoreBytes : pb::IMessage<MoreBytes>, pb::IMessage2 {
+  public sealed partial class MoreBytes : pb::IMessage<MoreBytes> {
     private static readonly pb::MessageParser<MoreBytes> _parser = new pb::MessageParser<MoreBytes>(() => new MoreBytes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4638,16 +4544,12 @@ public sealed partial class MoreBytes : pb::IMessage<MoreBytes>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test int32, uint32, int64, uint64, and bool are all compatible
   /// </summary>
-  public sealed partial class Int32Message : pb::IMessage<Int32Message>, pb::IMessage2 {
+  public sealed partial class Int32Message : pb::IMessage<Int32Message> {
     private static readonly pb::MessageParser<Int32Message> _parser = new pb::MessageParser<Int32Message>(() => new Int32Message());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4774,13 +4676,9 @@ public sealed partial class Int32Message : pb::IMessage<Int32Message>, pb::IMess
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class Uint32Message : pb::IMessage<Uint32Message>, pb::IMessage2 {
+  public sealed partial class Uint32Message : pb::IMessage<Uint32Message> {
     private static readonly pb::MessageParser<Uint32Message> _parser = new pb::MessageParser<Uint32Message>(() => new Uint32Message());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4907,13 +4805,9 @@ public sealed partial class Uint32Message : pb::IMessage<Uint32Message>, pb::IMe
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class Int64Message : pb::IMessage<Int64Message>, pb::IMessage2 {
+  public sealed partial class Int64Message : pb::IMessage<Int64Message> {
     private static readonly pb::MessageParser<Int64Message> _parser = new pb::MessageParser<Int64Message>(() => new Int64Message());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5040,13 +4934,9 @@ public sealed partial class Int64Message : pb::IMessage<Int64Message>, pb::IMess
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class Uint64Message : pb::IMessage<Uint64Message>, pb::IMessage2 {
+  public sealed partial class Uint64Message : pb::IMessage<Uint64Message> {
     private static readonly pb::MessageParser<Uint64Message> _parser = new pb::MessageParser<Uint64Message>(() => new Uint64Message());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5173,13 +5063,9 @@ public sealed partial class Uint64Message : pb::IMessage<Uint64Message>, pb::IMe
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class BoolMessage : pb::IMessage<BoolMessage>, pb::IMessage2 {
+  public sealed partial class BoolMessage : pb::IMessage<BoolMessage> {
     private static readonly pb::MessageParser<BoolMessage> _parser = new pb::MessageParser<BoolMessage>(() => new BoolMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5306,16 +5192,12 @@ public sealed partial class BoolMessage : pb::IMessage<BoolMessage>, pb::IMessag
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test oneofs.
   /// </summary>
-  public sealed partial class TestOneof : pb::IMessage<TestOneof>, pb::IMessage2 {
+  public sealed partial class TestOneof : pb::IMessage<TestOneof> {
     private static readonly pb::MessageParser<TestOneof> _parser = new pb::MessageParser<TestOneof>(() => new TestOneof());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5540,13 +5422,9 @@ public enum FooOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestPackedTypes : pb::IMessage<TestPackedTypes>, pb::IMessage2 {
+  public sealed partial class TestPackedTypes : pb::IMessage<TestPackedTypes> {
     private static readonly pb::MessageParser<TestPackedTypes> _parser = new pb::MessageParser<TestPackedTypes>(() => new TestPackedTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5939,17 +5817,13 @@ public sealed partial class TestPackedTypes : pb::IMessage<TestPackedTypes>, pb:
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// A message with the same fields as TestPackedTypes, but without packing. Used
   /// to test packed &lt;-> unpacked wire compatibility.
   /// </summary>
-  public sealed partial class TestUnpackedTypes : pb::IMessage<TestUnpackedTypes>, pb::IMessage2 {
+  public sealed partial class TestUnpackedTypes : pb::IMessage<TestUnpackedTypes> {
     private static readonly pb::MessageParser<TestUnpackedTypes> _parser = new pb::MessageParser<TestUnpackedTypes>(() => new TestUnpackedTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6342,13 +6216,9 @@ public sealed partial class TestUnpackedTypes : pb::IMessage<TestUnpackedTypes>,
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestRepeatedScalarDifferentTagSizes : pb::IMessage<TestRepeatedScalarDifferentTagSizes>, pb::IMessage2 {
+  public sealed partial class TestRepeatedScalarDifferentTagSizes : pb::IMessage<TestRepeatedScalarDifferentTagSizes> {
     private static readonly pb::MessageParser<TestRepeatedScalarDifferentTagSizes> _parser = new pb::MessageParser<TestRepeatedScalarDifferentTagSizes>(() => new TestRepeatedScalarDifferentTagSizes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6587,13 +6457,9 @@ public sealed partial class TestRepeatedScalarDifferentTagSizes : pb::IMessage<T
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestCommentInjectionMessage : pb::IMessage<TestCommentInjectionMessage>, pb::IMessage2 {
+  public sealed partial class TestCommentInjectionMessage : pb::IMessage<TestCommentInjectionMessage> {
     private static readonly pb::MessageParser<TestCommentInjectionMessage> _parser = new pb::MessageParser<TestCommentInjectionMessage>(() => new TestCommentInjectionMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6723,16 +6589,12 @@ public sealed partial class TestCommentInjectionMessage : pb::IMessage<TestComme
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// Test that RPC services work.
   /// </summary>
-  public sealed partial class FooRequest : pb::IMessage<FooRequest>, pb::IMessage2 {
+  public sealed partial class FooRequest : pb::IMessage<FooRequest> {
     private static readonly pb::MessageParser<FooRequest> _parser = new pb::MessageParser<FooRequest>(() => new FooRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6831,13 +6693,9 @@ public sealed partial class FooRequest : pb::IMessage<FooRequest>, pb::IMessage2
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class FooResponse : pb::IMessage<FooResponse>, pb::IMessage2 {
+  public sealed partial class FooResponse : pb::IMessage<FooResponse> {
     private static readonly pb::MessageParser<FooResponse> _parser = new pb::MessageParser<FooResponse>(() => new FooResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6936,13 +6794,9 @@ public sealed partial class FooResponse : pb::IMessage<FooResponse>, pb::IMessag
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class FooClientMessage : pb::IMessage<FooClientMessage>, pb::IMessage2 {
+  public sealed partial class FooClientMessage : pb::IMessage<FooClientMessage> {
     private static readonly pb::MessageParser<FooClientMessage> _parser = new pb::MessageParser<FooClientMessage>(() => new FooClientMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7041,13 +6895,9 @@ public sealed partial class FooClientMessage : pb::IMessage<FooClientMessage>, p
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class FooServerMessage : pb::IMessage<FooServerMessage>, pb::IMessage2 {
+  public sealed partial class FooServerMessage : pb::IMessage<FooServerMessage> {
     private static readonly pb::MessageParser<FooServerMessage> _parser = new pb::MessageParser<FooServerMessage>(() => new FooServerMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7146,13 +6996,9 @@ public sealed partial class FooServerMessage : pb::IMessage<FooServerMessage>, p
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class BarRequest : pb::IMessage<BarRequest>, pb::IMessage2 {
+  public sealed partial class BarRequest : pb::IMessage<BarRequest> {
     private static readonly pb::MessageParser<BarRequest> _parser = new pb::MessageParser<BarRequest>(() => new BarRequest());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7251,13 +7097,9 @@ public sealed partial class BarRequest : pb::IMessage<BarRequest>, pb::IMessage2
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class BarResponse : pb::IMessage<BarResponse>, pb::IMessage2 {
+  public sealed partial class BarResponse : pb::IMessage<BarResponse> {
     private static readonly pb::MessageParser<BarResponse> _parser = new pb::MessageParser<BarResponse>(() => new BarResponse());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7356,13 +7198,9 @@ public sealed partial class BarResponse : pb::IMessage<BarResponse>, pb::IMessag
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
-  public sealed partial class TestEmptyMessage : pb::IMessage<TestEmptyMessage>, pb::IMessage2 {
+  public sealed partial class TestEmptyMessage : pb::IMessage<TestEmptyMessage> {
     private static readonly pb::MessageParser<TestEmptyMessage> _parser = new pb::MessageParser<TestEmptyMessage>(() => new TestEmptyMessage());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7461,10 +7299,6 @@ public sealed partial class TestEmptyMessage : pb::IMessage<TestEmptyMessage>, p
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestWellKnownTypes.cs b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestWellKnownTypes.cs
index 131a45f7c05e..45f8ece64695 100644
--- a/csharp/src/Google.Protobuf.Test/TestProtos/UnittestWellKnownTypes.cs
+++ b/csharp/src/Google.Protobuf.Test/TestProtos/UnittestWellKnownTypes.cs
@@ -179,7 +179,7 @@ public static partial class UnittestWellKnownTypesReflection {
   /// Each wrapper type is included separately, as languages
   /// map handle different wrappers in different ways.
   /// </summary>
-  public sealed partial class TestWellKnownTypes : pb::IMessage<TestWellKnownTypes>, pb::IMessage2 {
+  public sealed partial class TestWellKnownTypes : pb::IMessage<TestWellKnownTypes> {
     private static readonly pb::MessageParser<TestWellKnownTypes> _parser = new pb::MessageParser<TestWellKnownTypes>(() => new TestWellKnownTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -927,16 +927,12 @@ public sealed partial class TestWellKnownTypes : pb::IMessage<TestWellKnownTypes
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
   /// A repeated field for each well-known type.
   /// </summary>
-  public sealed partial class RepeatedWellKnownTypes : pb::IMessage<RepeatedWellKnownTypes>, pb::IMessage2 {
+  public sealed partial class RepeatedWellKnownTypes : pb::IMessage<RepeatedWellKnownTypes> {
     private static readonly pb::MessageParser<RepeatedWellKnownTypes> _parser = new pb::MessageParser<RepeatedWellKnownTypes>(() => new RepeatedWellKnownTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1398,67 +1394,9 @@ public sealed partial class RepeatedWellKnownTypes : pb::IMessage<RepeatedWellKn
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!anyField_.IsInitialized()) {
-        return false;
-      }
-      if (!apiField_.IsInitialized()) {
-        return false;
-      }
-      if (!durationField_.IsInitialized()) {
-        return false;
-      }
-      if (!emptyField_.IsInitialized()) {
-        return false;
-      }
-      if (!fieldMaskField_.IsInitialized()) {
-        return false;
-      }
-      if (!sourceContextField_.IsInitialized()) {
-        return false;
-      }
-      if (!structField_.IsInitialized()) {
-        return false;
-      }
-      if (!timestampField_.IsInitialized()) {
-        return false;
-      }
-      if (!typeField_.IsInitialized()) {
-        return false;
-      }
-      if (!doubleField_.IsInitialized()) {
-        return false;
-      }
-      if (!floatField_.IsInitialized()) {
-        return false;
-      }
-      if (!int64Field_.IsInitialized()) {
-        return false;
-      }
-      if (!uint64Field_.IsInitialized()) {
-        return false;
-      }
-      if (!int32Field_.IsInitialized()) {
-        return false;
-      }
-      if (!uint32Field_.IsInitialized()) {
-        return false;
-      }
-      if (!boolField_.IsInitialized()) {
-        return false;
-      }
-      if (!stringField_.IsInitialized()) {
-        return false;
-      }
-      if (!bytesField_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  public sealed partial class OneofWellKnownTypes : pb::IMessage<OneofWellKnownTypes>, pb::IMessage2 {
+  public sealed partial class OneofWellKnownTypes : pb::IMessage<OneofWellKnownTypes> {
     private static readonly pb::MessageParser<OneofWellKnownTypes> _parser = new pb::MessageParser<OneofWellKnownTypes>(() => new OneofWellKnownTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2212,10 +2150,6 @@ public enum OneofFieldOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -2223,7 +2157,7 @@ public enum OneofFieldOneofCase {
   /// need to worry about the value part of the map being the
   /// well-known types, as messages can't be map keys.
   /// </summary>
-  public sealed partial class MapWellKnownTypes : pb::IMessage<MapWellKnownTypes>, pb::IMessage2 {
+  public sealed partial class MapWellKnownTypes : pb::IMessage<MapWellKnownTypes> {
     private static readonly pb::MessageParser<MapWellKnownTypes> _parser = new pb::MessageParser<MapWellKnownTypes>(() => new MapWellKnownTypes());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2682,64 +2616,6 @@ public sealed partial class MapWellKnownTypes : pb::IMessage<MapWellKnownTypes>,
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!anyField_.IsInitialized()) {
-        return false;
-      }
-      if (!apiField_.IsInitialized()) {
-        return false;
-      }
-      if (!durationField_.IsInitialized()) {
-        return false;
-      }
-      if (!emptyField_.IsInitialized()) {
-        return false;
-      }
-      if (!fieldMaskField_.IsInitialized()) {
-        return false;
-      }
-      if (!sourceContextField_.IsInitialized()) {
-        return false;
-      }
-      if (!structField_.IsInitialized()) {
-        return false;
-      }
-      if (!timestampField_.IsInitialized()) {
-        return false;
-      }
-      if (!typeField_.IsInitialized()) {
-        return false;
-      }
-      if (!doubleField_.IsInitialized()) {
-        return false;
-      }
-      if (!floatField_.IsInitialized()) {
-        return false;
-      }
-      if (!int64Field_.IsInitialized()) {
-        return false;
-      }
-      if (!uint64Field_.IsInitialized()) {
-        return false;
-      }
-      if (!int32Field_.IsInitialized()) {
-        return false;
-      }
-      if (!uint32Field_.IsInitialized()) {
-        return false;
-      }
-      if (!boolField_.IsInitialized()) {
-        return false;
-      }
-      if (!stringField_.IsInitialized()) {
-        return false;
-      }
-      if (!bytesField_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/Reflection/Descriptor.cs b/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
index 7320a87e0848..0c33e63df46a 100644
--- a/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
+++ b/csharp/src/Google.Protobuf/Reflection/Descriptor.cs
@@ -193,7 +193,7 @@ internal static partial class DescriptorReflection {
   /// The protocol compiler can output a FileDescriptorSet containing the .proto
   /// files it parses.
   /// </summary>
-  internal sealed partial class FileDescriptorSet : pb::IMessage<FileDescriptorSet>, pb::IMessage2 {
+  internal sealed partial class FileDescriptorSet : pb::IMessage<FileDescriptorSet> {
     private static readonly pb::MessageParser<FileDescriptorSet> _parser = new pb::MessageParser<FileDescriptorSet>(() => new FileDescriptorSet());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -312,19 +312,12 @@ internal sealed partial class FileDescriptorSet : pb::IMessage<FileDescriptorSet
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!file_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Describes a complete .proto file.
   /// </summary>
-  internal sealed partial class FileDescriptorProto : pb::IMessage<FileDescriptorProto>, pb::IMessage2 {
+  internal sealed partial class FileDescriptorProto : pb::IMessage<FileDescriptorProto> {
     private static readonly pb::MessageParser<FileDescriptorProto> _parser = new pb::MessageParser<FileDescriptorProto>(() => new FileDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -802,38 +795,12 @@ internal sealed partial class FileDescriptorProto : pb::IMessage<FileDescriptorP
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!messageType_.IsInitialized()) {
-        return false;
-      }
-      if (!enumType_.IsInitialized()) {
-        return false;
-      }
-      if (!service_.IsInitialized()) {
-        return false;
-      }
-      if (!extension_.IsInitialized()) {
-        return false;
-      }
-      if (HasOptions) {
-        if (!Options.IsInitialized()) {
-          return false;
-        }
-      }
-      if (HasSourceCodeInfo) {
-        if (!SourceCodeInfo.IsInitialized()) {
-          return false;
-        }
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Describes a message type.
   /// </summary>
-  internal sealed partial class DescriptorProto : pb::IMessage<DescriptorProto>, pb::IMessage2 {
+  internal sealed partial class DescriptorProto : pb::IMessage<DescriptorProto> {
     private static readonly pb::MessageParser<DescriptorProto> _parser = new pb::MessageParser<DescriptorProto>(() => new DescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1180,41 +1147,11 @@ internal sealed partial class DescriptorProto : pb::IMessage<DescriptorProto>, p
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!field_.IsInitialized()) {
-        return false;
-      }
-      if (!nestedType_.IsInitialized()) {
-        return false;
-      }
-      if (!enumType_.IsInitialized()) {
-        return false;
-      }
-      if (!extensionRange_.IsInitialized()) {
-        return false;
-      }
-      if (!extension_.IsInitialized()) {
-        return false;
-      }
-      if (HasOptions) {
-        if (!Options.IsInitialized()) {
-          return false;
-        }
-      }
-      if (!oneofDecl_.IsInitialized()) {
-        return false;
-      }
-      if (!reservedRange_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the DescriptorProto message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      internal sealed partial class ExtensionRange : pb::IMessage<ExtensionRange>, pb::IMessage2 {
+      internal sealed partial class ExtensionRange : pb::IMessage<ExtensionRange> {
         private static readonly pb::MessageParser<ExtensionRange> _parser = new pb::MessageParser<ExtensionRange>(() => new ExtensionRange());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -1441,15 +1378,6 @@ internal sealed partial class ExtensionRange : pb::IMessage<ExtensionRange>, pb:
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          if (HasOptions) {
-            if (!Options.IsInitialized()) {
-              return false;
-            }
-          }
-          return true;
-        }
       }
 
       /// <summary>
@@ -1457,7 +1385,7 @@ internal sealed partial class ExtensionRange : pb::IMessage<ExtensionRange>, pb:
       /// fields or extension ranges in the same message. Reserved ranges may
       /// not overlap.
       /// </summary>
-      internal sealed partial class ReservedRange : pb::IMessage<ReservedRange>, pb::IMessage2 {
+      internal sealed partial class ReservedRange : pb::IMessage<ReservedRange> {
         private static readonly pb::MessageParser<ReservedRange> _parser = new pb::MessageParser<ReservedRange>(() => new ReservedRange());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -1646,10 +1574,6 @@ internal sealed partial class ReservedRange : pb::IMessage<ReservedRange>, pb::I
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -1657,7 +1581,7 @@ internal sealed partial class ReservedRange : pb::IMessage<ReservedRange>, pb::I
 
   }
 
-  internal sealed partial class ExtensionRangeOptions : pb::IMessage<ExtensionRangeOptions>, pb::IMessage2 {
+  internal sealed partial class ExtensionRangeOptions : pb::IMessage<ExtensionRangeOptions> {
     private static readonly pb::MessageParser<ExtensionRangeOptions> _parser = new pb::MessageParser<ExtensionRangeOptions>(() => new ExtensionRangeOptions());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1779,19 +1703,12 @@ internal sealed partial class ExtensionRangeOptions : pb::IMessage<ExtensionRang
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Describes a field within a message.
   /// </summary>
-  internal sealed partial class FieldDescriptorProto : pb::IMessage<FieldDescriptorProto>, pb::IMessage2 {
+  internal sealed partial class FieldDescriptorProto : pb::IMessage<FieldDescriptorProto> {
     private static readonly pb::MessageParser<FieldDescriptorProto> _parser = new pb::MessageParser<FieldDescriptorProto>(() => new FieldDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -2332,15 +2249,6 @@ internal sealed partial class FieldDescriptorProto : pb::IMessage<FieldDescripto
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (HasOptions) {
-        if (!Options.IsInitialized()) {
-          return false;
-        }
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the FieldDescriptorProto message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2413,7 +2321,7 @@ internal enum Label {
   /// <summary>
   /// Describes a oneof.
   /// </summary>
-  internal sealed partial class OneofDescriptorProto : pb::IMessage<OneofDescriptorProto>, pb::IMessage2 {
+  internal sealed partial class OneofDescriptorProto : pb::IMessage<OneofDescriptorProto> {
     private static readonly pb::MessageParser<OneofDescriptorProto> _parser = new pb::MessageParser<OneofDescriptorProto>(() => new OneofDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2596,21 +2504,12 @@ internal sealed partial class OneofDescriptorProto : pb::IMessage<OneofDescripto
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (HasOptions) {
-        if (!Options.IsInitialized()) {
-          return false;
-        }
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Describes an enum type.
   /// </summary>
-  internal sealed partial class EnumDescriptorProto : pb::IMessage<EnumDescriptorProto>, pb::IMessage2 {
+  internal sealed partial class EnumDescriptorProto : pb::IMessage<EnumDescriptorProto> {
     private static readonly pb::MessageParser<EnumDescriptorProto> _parser = new pb::MessageParser<EnumDescriptorProto>(() => new EnumDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2862,21 +2761,6 @@ internal sealed partial class EnumDescriptorProto : pb::IMessage<EnumDescriptorP
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!value_.IsInitialized()) {
-        return false;
-      }
-      if (HasOptions) {
-        if (!Options.IsInitialized()) {
-          return false;
-        }
-      }
-      if (!reservedRange_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the EnumDescriptorProto message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -2889,7 +2773,7 @@ public static partial class Types {
       /// is inclusive such that it can appropriately represent the entire int32
       /// domain.
       /// </summary>
-      internal sealed partial class EnumReservedRange : pb::IMessage<EnumReservedRange>, pb::IMessage2 {
+      internal sealed partial class EnumReservedRange : pb::IMessage<EnumReservedRange> {
         private static readonly pb::MessageParser<EnumReservedRange> _parser = new pb::MessageParser<EnumReservedRange>(() => new EnumReservedRange());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -3078,10 +2962,6 @@ internal sealed partial class EnumReservedRange : pb::IMessage<EnumReservedRange
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -3092,7 +2972,7 @@ internal sealed partial class EnumReservedRange : pb::IMessage<EnumReservedRange
   /// <summary>
   /// Describes a value within an enum.
   /// </summary>
-  internal sealed partial class EnumValueDescriptorProto : pb::IMessage<EnumValueDescriptorProto>, pb::IMessage2 {
+  internal sealed partial class EnumValueDescriptorProto : pb::IMessage<EnumValueDescriptorProto> {
     private static readonly pb::MessageParser<EnumValueDescriptorProto> _parser = new pb::MessageParser<EnumValueDescriptorProto>(() => new EnumValueDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -3318,21 +3198,12 @@ internal sealed partial class EnumValueDescriptorProto : pb::IMessage<EnumValueD
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (HasOptions) {
-        if (!Options.IsInitialized()) {
-          return false;
-        }
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Describes a service.
   /// </summary>
-  internal sealed partial class ServiceDescriptorProto : pb::IMessage<ServiceDescriptorProto>, pb::IMessage2 {
+  internal sealed partial class ServiceDescriptorProto : pb::IMessage<ServiceDescriptorProto> {
     private static readonly pb::MessageParser<ServiceDescriptorProto> _parser = new pb::MessageParser<ServiceDescriptorProto>(() => new ServiceDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -3535,24 +3406,12 @@ internal sealed partial class ServiceDescriptorProto : pb::IMessage<ServiceDescr
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!method_.IsInitialized()) {
-        return false;
-      }
-      if (HasOptions) {
-        if (!Options.IsInitialized()) {
-          return false;
-        }
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Describes a method of a service.
   /// </summary>
-  internal sealed partial class MethodDescriptorProto : pb::IMessage<MethodDescriptorProto>, pb::IMessage2 {
+  internal sealed partial class MethodDescriptorProto : pb::IMessage<MethodDescriptorProto> {
     private static readonly pb::MessageParser<MethodDescriptorProto> _parser = new pb::MessageParser<MethodDescriptorProto>(() => new MethodDescriptorProto());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -3909,18 +3768,9 @@ internal sealed partial class MethodDescriptorProto : pb::IMessage<MethodDescrip
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (HasOptions) {
-        if (!Options.IsInitialized()) {
-          return false;
-        }
-      }
-      return true;
-    }
   }
 
-  internal sealed partial class FileOptions : pb::IMessage<FileOptions>, pb::IMessage2 {
+  internal sealed partial class FileOptions : pb::IMessage<FileOptions> {
     private static readonly pb::MessageParser<FileOptions> _parser = new pb::MessageParser<FileOptions>(() => new FileOptions());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -4953,13 +4803,6 @@ internal sealed partial class FileOptions : pb::IMessage<FileOptions>, pb::IMess
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the FileOptions message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -4987,7 +4830,7 @@ internal enum OptimizeMode {
 
   }
 
-  internal sealed partial class MessageOptions : pb::IMessage<MessageOptions>, pb::IMessage2 {
+  internal sealed partial class MessageOptions : pb::IMessage<MessageOptions> {
     private static readonly pb::MessageParser<MessageOptions> _parser = new pb::MessageParser<MessageOptions>(() => new MessageOptions());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -5331,16 +5174,9 @@ internal sealed partial class MessageOptions : pb::IMessage<MessageOptions>, pb:
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  internal sealed partial class FieldOptions : pb::IMessage<FieldOptions>, pb::IMessage2 {
+  internal sealed partial class FieldOptions : pb::IMessage<FieldOptions> {
     private static readonly pb::MessageParser<FieldOptions> _parser = new pb::MessageParser<FieldOptions>(() => new FieldOptions());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -5776,13 +5612,6 @@ internal sealed partial class FieldOptions : pb::IMessage<FieldOptions>, pb::IMe
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the FieldOptions message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5816,7 +5645,7 @@ internal enum JSType {
 
   }
 
-  internal sealed partial class OneofOptions : pb::IMessage<OneofOptions>, pb::IMessage2 {
+  internal sealed partial class OneofOptions : pb::IMessage<OneofOptions> {
     private static readonly pb::MessageParser<OneofOptions> _parser = new pb::MessageParser<OneofOptions>(() => new OneofOptions());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -5940,16 +5769,9 @@ internal sealed partial class OneofOptions : pb::IMessage<OneofOptions>, pb::IMe
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  internal sealed partial class EnumOptions : pb::IMessage<EnumOptions>, pb::IMessage2 {
+  internal sealed partial class EnumOptions : pb::IMessage<EnumOptions> {
     private static readonly pb::MessageParser<EnumOptions> _parser = new pb::MessageParser<EnumOptions>(() => new EnumOptions());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -6167,16 +5989,9 @@ internal sealed partial class EnumOptions : pb::IMessage<EnumOptions>, pb::IMess
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  internal sealed partial class EnumValueOptions : pb::IMessage<EnumValueOptions>, pb::IMessage2 {
+  internal sealed partial class EnumValueOptions : pb::IMessage<EnumValueOptions> {
     private static readonly pb::MessageParser<EnumValueOptions> _parser = new pb::MessageParser<EnumValueOptions>(() => new EnumValueOptions());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -6349,16 +6164,9 @@ internal sealed partial class EnumValueOptions : pb::IMessage<EnumValueOptions>,
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  internal sealed partial class ServiceOptions : pb::IMessage<ServiceOptions>, pb::IMessage2 {
+  internal sealed partial class ServiceOptions : pb::IMessage<ServiceOptions> {
     private static readonly pb::MessageParser<ServiceOptions> _parser = new pb::MessageParser<ServiceOptions>(() => new ServiceOptions());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -6531,16 +6339,9 @@ internal sealed partial class ServiceOptions : pb::IMessage<ServiceOptions>, pb:
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
-  internal sealed partial class MethodOptions : pb::IMessage<MethodOptions>, pb::IMessage2 {
+  internal sealed partial class MethodOptions : pb::IMessage<MethodOptions> {
     private static readonly pb::MessageParser<MethodOptions> _parser = new pb::MessageParser<MethodOptions>(() => new MethodOptions());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -6754,13 +6555,6 @@ internal sealed partial class MethodOptions : pb::IMessage<MethodOptions>, pb::I
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!uninterpretedOption_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the MethodOptions message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -6795,7 +6589,7 @@ internal enum IdempotencyLevel {
   /// or produced by Descriptor::CopyTo()) will never have UninterpretedOptions
   /// in them.
   /// </summary>
-  internal sealed partial class UninterpretedOption : pb::IMessage<UninterpretedOption>, pb::IMessage2 {
+  internal sealed partial class UninterpretedOption : pb::IMessage<UninterpretedOption> {
     private static readonly pb::MessageParser<UninterpretedOption> _parser = new pb::MessageParser<UninterpretedOption>(() => new UninterpretedOption());
     private pb::UnknownFieldSet _unknownFields;
     private int _hasBits0;
@@ -7163,13 +6957,6 @@ internal sealed partial class UninterpretedOption : pb::IMessage<UninterpretedOp
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!name_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the UninterpretedOption message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7181,7 +6968,7 @@ public static partial class Types {
       /// E.g.,{ ["foo", false], ["bar.baz", true], ["qux", false] } represents
       /// "foo.(bar.baz).qux".
       /// </summary>
-      internal sealed partial class NamePart : pb::IMessage<NamePart>, pb::IMessage2 {
+      internal sealed partial class NamePart : pb::IMessage<NamePart> {
         private static readonly pb::MessageParser<NamePart> _parser = new pb::MessageParser<NamePart>(() => new NamePart());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -7363,16 +7150,6 @@ internal sealed partial class NamePart : pb::IMessage<NamePart>, pb::IMessage2 {
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          if (!!HasNamePart_) {
-            return false;
-          }
-          if (!!HasIsExtension) {
-            return false;
-          }
-          return true;
-        }
       }
 
     }
@@ -7384,7 +7161,7 @@ internal sealed partial class NamePart : pb::IMessage<NamePart>, pb::IMessage2 {
   /// Encapsulates information about the original source file from which a
   /// FileDescriptorProto was generated.
   /// </summary>
-  internal sealed partial class SourceCodeInfo : pb::IMessage<SourceCodeInfo>, pb::IMessage2 {
+  internal sealed partial class SourceCodeInfo : pb::IMessage<SourceCodeInfo> {
     private static readonly pb::MessageParser<SourceCodeInfo> _parser = new pb::MessageParser<SourceCodeInfo>(() => new SourceCodeInfo());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7548,18 +7325,11 @@ internal sealed partial class SourceCodeInfo : pb::IMessage<SourceCodeInfo>, pb:
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!location_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the SourceCodeInfo message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      internal sealed partial class Location : pb::IMessage<Location>, pb::IMessage2 {
+      internal sealed partial class Location : pb::IMessage<Location> {
         private static readonly pb::MessageParser<Location> _parser = new pb::MessageParser<Location>(() => new Location());
         private pb::UnknownFieldSet _unknownFields;
         [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -7881,10 +7651,6 @@ internal sealed partial class Location : pb::IMessage<Location>, pb::IMessage2 {
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
@@ -7897,7 +7663,7 @@ internal sealed partial class Location : pb::IMessage<Location>, pb::IMessage2 {
   /// file. A GeneratedCodeInfo message is associated with only one generated
   /// source file, but may contain references to different source .proto files.
   /// </summary>
-  internal sealed partial class GeneratedCodeInfo : pb::IMessage<GeneratedCodeInfo>, pb::IMessage2 {
+  internal sealed partial class GeneratedCodeInfo : pb::IMessage<GeneratedCodeInfo> {
     private static readonly pb::MessageParser<GeneratedCodeInfo> _parser = new pb::MessageParser<GeneratedCodeInfo>(() => new GeneratedCodeInfo());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -8020,18 +7786,11 @@ internal sealed partial class GeneratedCodeInfo : pb::IMessage<GeneratedCodeInfo
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!annotation_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the GeneratedCodeInfo message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     public static partial class Types {
-      internal sealed partial class Annotation : pb::IMessage<Annotation>, pb::IMessage2 {
+      internal sealed partial class Annotation : pb::IMessage<Annotation> {
         private static readonly pb::MessageParser<Annotation> _parser = new pb::MessageParser<Annotation>(() => new Annotation());
         private pb::UnknownFieldSet _unknownFields;
         private int _hasBits0;
@@ -8291,10 +8050,6 @@ internal sealed partial class Annotation : pb::IMessage<Annotation>, pb::IMessag
           }
         }
 
-        [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-        public bool IsInitialized() {
-          return true;
-        }
       }
 
     }
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
index f541f411522a..dd9911067ed9 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Any.cs
@@ -119,7 +119,7 @@ public static partial class AnyReflection {
   ///       "value": "1.212s"
   ///     }
   /// </summary>
-  public sealed partial class Any : pb::IMessage<Any>, pb::IMessage2 {
+  public sealed partial class Any : pb::IMessage<Any> {
     private static readonly pb::MessageParser<Any> _parser = new pb::MessageParser<Any>(() => new Any());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -306,10 +306,6 @@ public sealed partial class Any : pb::IMessage<Any>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
index 9e20d6f8f38d..438e1db8da2f 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Api.cs
@@ -64,7 +64,7 @@ public static partial class ApiReflection {
   /// this message itself. See https://cloud.google.com/apis/design/glossary for
   /// detailed terminology.
   /// </summary>
-  public sealed partial class Api : pb::IMessage<Api>, pb::IMessage2 {
+  public sealed partial class Api : pb::IMessage<Api> {
     private static readonly pb::MessageParser<Api> _parser = new pb::MessageParser<Api>(() => new Api());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -382,25 +382,12 @@ public sealed partial class Api : pb::IMessage<Api>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!methods_.IsInitialized()) {
-        return false;
-      }
-      if (!options_.IsInitialized()) {
-        return false;
-      }
-      if (!mixins_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Method represents a method of an API interface.
   /// </summary>
-  public sealed partial class Method : pb::IMessage<Method>, pb::IMessage2 {
+  public sealed partial class Method : pb::IMessage<Method> {
     private static readonly pb::MessageParser<Method> _parser = new pb::MessageParser<Method>(() => new Method());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -708,13 +695,6 @@ public sealed partial class Method : pb::IMessage<Method>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!options_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
@@ -797,7 +777,7 @@ public sealed partial class Method : pb::IMessage<Method>, pb::IMessage2 {
   ///       ...
   ///     }
   /// </summary>
-  public sealed partial class Mixin : pb::IMessage<Mixin>, pb::IMessage2 {
+  public sealed partial class Mixin : pb::IMessage<Mixin> {
     private static readonly pb::MessageParser<Mixin> _parser = new pb::MessageParser<Mixin>(() => new Mixin());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -959,10 +939,6 @@ public sealed partial class Mixin : pb::IMessage<Mixin>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
index 3e7eb46ebc23..2858b532b636 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Duration.cs
@@ -100,7 +100,7 @@ public static partial class DurationReflection {
   /// be expressed in JSON format as "3.000000001s", and 3 seconds and 1
   /// microsecond should be expressed in JSON format as "3.000001s".
   /// </summary>
-  public sealed partial class Duration : pb::IMessage<Duration>, pb::IMessage2 {
+  public sealed partial class Duration : pb::IMessage<Duration> {
     private static readonly pb::MessageParser<Duration> _parser = new pb::MessageParser<Duration>(() => new Duration());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -268,10 +268,6 @@ public sealed partial class Duration : pb::IMessage<Duration>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
index ce8859fc5d25..2113add9bca1 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Empty.cs
@@ -50,7 +50,7 @@ public static partial class EmptyReflection {
   ///
   /// The JSON representation for `Empty` is empty JSON object `{}`.
   /// </summary>
-  public sealed partial class Empty : pb::IMessage<Empty>, pb::IMessage2 {
+  public sealed partial class Empty : pb::IMessage<Empty> {
     private static readonly pb::MessageParser<Empty> _parser = new pb::MessageParser<Empty>(() => new Empty());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -149,10 +149,6 @@ public sealed partial class Empty : pb::IMessage<Empty>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs b/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
index 8698baa4a8a6..6ad31a50eacc 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/FieldMask.cs
@@ -240,7 +240,7 @@ public static partial class FieldMaskReflection {
   /// request should verify the included field paths, and return an
   /// `INVALID_ARGUMENT` error if any path is duplicated or unmappable.
   /// </summary>
-  public sealed partial class FieldMask : pb::IMessage<FieldMask>, pb::IMessage2 {
+  public sealed partial class FieldMask : pb::IMessage<FieldMask> {
     private static readonly pb::MessageParser<FieldMask> _parser = new pb::MessageParser<FieldMask>(() => new FieldMask());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -362,10 +362,6 @@ public sealed partial class FieldMask : pb::IMessage<FieldMask>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs b/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
index 53dd49026826..124ddaa71234 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/SourceContext.cs
@@ -44,7 +44,7 @@ public static partial class SourceContextReflection {
   /// `SourceContext` represents information about the source of a
   /// protobuf element, like the file in which it is defined.
   /// </summary>
-  public sealed partial class SourceContext : pb::IMessage<SourceContext>, pb::IMessage2 {
+  public sealed partial class SourceContext : pb::IMessage<SourceContext> {
     private static readonly pb::MessageParser<SourceContext> _parser = new pb::MessageParser<SourceContext>(() => new SourceContext());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -175,10 +175,6 @@ public sealed partial class SourceContext : pb::IMessage<SourceContext>, pb::IMe
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
index 0539cad99dfb..194b81e965e5 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Struct.cs
@@ -77,7 +77,7 @@ public enum NullValue {
   ///
   /// The JSON representation for `Struct` is JSON object.
   /// </summary>
-  public sealed partial class Struct : pb::IMessage<Struct>, pb::IMessage2 {
+  public sealed partial class Struct : pb::IMessage<Struct> {
     private static readonly pb::MessageParser<Struct> _parser = new pb::MessageParser<Struct>(() => new Struct());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -199,13 +199,6 @@ public sealed partial class Struct : pb::IMessage<Struct>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!fields_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
@@ -216,7 +209,7 @@ public sealed partial class Struct : pb::IMessage<Struct>, pb::IMessage2 {
   ///
   /// The JSON representation for `Value` is JSON value.
   /// </summary>
-  public sealed partial class Value : pb::IMessage<Value>, pb::IMessage2 {
+  public sealed partial class Value : pb::IMessage<Value> {
     private static readonly pb::MessageParser<Value> _parser = new pb::MessageParser<Value>(() => new Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -561,10 +554,6 @@ public enum KindOneofCase {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -572,7 +561,7 @@ public enum KindOneofCase {
   ///
   /// The JSON representation for `ListValue` is JSON array.
   /// </summary>
-  public sealed partial class ListValue : pb::IMessage<ListValue>, pb::IMessage2 {
+  public sealed partial class ListValue : pb::IMessage<ListValue> {
     private static readonly pb::MessageParser<ListValue> _parser = new pb::MessageParser<ListValue>(() => new ListValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -694,13 +683,6 @@ public sealed partial class ListValue : pb::IMessage<ListValue>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!values_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
index c863d45f682a..d1ab0f8965df 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Timestamp.cs
@@ -119,7 +119,7 @@ public static partial class TimestampReflection {
   /// http://www.joda.org/joda-time/apidocs/org/joda/time/format/ISODateTimeFormat.html#dateTime%2D%2D
   /// ) to obtain a formatter capable of generating timestamps in this format.
   /// </summary>
-  public sealed partial class Timestamp : pb::IMessage<Timestamp>, pb::IMessage2 {
+  public sealed partial class Timestamp : pb::IMessage<Timestamp> {
     private static readonly pb::MessageParser<Timestamp> _parser = new pb::MessageParser<Timestamp>(() => new Timestamp());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -285,10 +285,6 @@ public sealed partial class Timestamp : pb::IMessage<Timestamp>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
index 1e22650c9ae3..52bd343ba841 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Type.cs
@@ -94,7 +94,7 @@ public enum Syntax {
   /// <summary>
   /// A protocol buffer message type.
   /// </summary>
-  public sealed partial class Type : pb::IMessage<Type>, pb::IMessage2 {
+  public sealed partial class Type : pb::IMessage<Type> {
     private static readonly pb::MessageParser<Type> _parser = new pb::MessageParser<Type>(() => new Type());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -361,22 +361,12 @@ public sealed partial class Type : pb::IMessage<Type>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!fields_.IsInitialized()) {
-        return false;
-      }
-      if (!options_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// A single field of a message type.
   /// </summary>
-  public sealed partial class Field : pb::IMessage<Field>, pb::IMessage2 {
+  public sealed partial class Field : pb::IMessage<Field> {
     private static readonly pb::MessageParser<Field> _parser = new pb::MessageParser<Field>(() => new Field());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -779,13 +769,6 @@ public sealed partial class Field : pb::IMessage<Field>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!options_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
     #region Nested types
     /// <summary>Container for nested types declared in the Field message type.</summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -902,7 +885,7 @@ public enum Cardinality {
   /// <summary>
   /// Enum type definition.
   /// </summary>
-  public sealed partial class Enum : pb::IMessage<Enum>, pb::IMessage2 {
+  public sealed partial class Enum : pb::IMessage<Enum> {
     private static readonly pb::MessageParser<Enum> _parser = new pb::MessageParser<Enum>(() => new Enum());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1146,22 +1129,12 @@ public sealed partial class Enum : pb::IMessage<Enum>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!enumvalue_.IsInitialized()) {
-        return false;
-      }
-      if (!options_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// Enum value definition.
   /// </summary>
-  public sealed partial class EnumValue : pb::IMessage<EnumValue>, pb::IMessage2 {
+  public sealed partial class EnumValue : pb::IMessage<EnumValue> {
     private static readonly pb::MessageParser<EnumValue> _parser = new pb::MessageParser<EnumValue>(() => new EnumValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1345,20 +1318,13 @@ public sealed partial class EnumValue : pb::IMessage<EnumValue>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      if (!options_.IsInitialized()) {
-        return false;
-      }
-      return true;
-    }
   }
 
   /// <summary>
   /// A protocol buffer option, which can be attached to a message, field,
   /// enumeration, etc.
   /// </summary>
-  public sealed partial class Option : pb::IMessage<Option>, pb::IMessage2 {
+  public sealed partial class Option : pb::IMessage<Option> {
     private static readonly pb::MessageParser<Option> _parser = new pb::MessageParser<Option>(() => new Option());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1531,10 +1497,6 @@ public sealed partial class Option : pb::IMessage<Option>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion
diff --git a/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs b/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
index 152c1c7b4d4f..25a65aa72c98 100644
--- a/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
+++ b/csharp/src/Google.Protobuf/WellKnownTypes/Wrappers.cs
@@ -57,7 +57,7 @@ public static partial class WrappersReflection {
   ///
   /// The JSON representation for `DoubleValue` is JSON number.
   /// </summary>
-  public sealed partial class DoubleValue : pb::IMessage<DoubleValue>, pb::IMessage2 {
+  public sealed partial class DoubleValue : pb::IMessage<DoubleValue> {
     private static readonly pb::MessageParser<DoubleValue> _parser = new pb::MessageParser<DoubleValue>(() => new DoubleValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -187,10 +187,6 @@ public sealed partial class DoubleValue : pb::IMessage<DoubleValue>, pb::IMessag
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -198,7 +194,7 @@ public sealed partial class DoubleValue : pb::IMessage<DoubleValue>, pb::IMessag
   ///
   /// The JSON representation for `FloatValue` is JSON number.
   /// </summary>
-  public sealed partial class FloatValue : pb::IMessage<FloatValue>, pb::IMessage2 {
+  public sealed partial class FloatValue : pb::IMessage<FloatValue> {
     private static readonly pb::MessageParser<FloatValue> _parser = new pb::MessageParser<FloatValue>(() => new FloatValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -328,10 +324,6 @@ public sealed partial class FloatValue : pb::IMessage<FloatValue>, pb::IMessage2
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -339,7 +331,7 @@ public sealed partial class FloatValue : pb::IMessage<FloatValue>, pb::IMessage2
   ///
   /// The JSON representation for `Int64Value` is JSON string.
   /// </summary>
-  public sealed partial class Int64Value : pb::IMessage<Int64Value>, pb::IMessage2 {
+  public sealed partial class Int64Value : pb::IMessage<Int64Value> {
     private static readonly pb::MessageParser<Int64Value> _parser = new pb::MessageParser<Int64Value>(() => new Int64Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -469,10 +461,6 @@ public sealed partial class Int64Value : pb::IMessage<Int64Value>, pb::IMessage2
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -480,7 +468,7 @@ public sealed partial class Int64Value : pb::IMessage<Int64Value>, pb::IMessage2
   ///
   /// The JSON representation for `UInt64Value` is JSON string.
   /// </summary>
-  public sealed partial class UInt64Value : pb::IMessage<UInt64Value>, pb::IMessage2 {
+  public sealed partial class UInt64Value : pb::IMessage<UInt64Value> {
     private static readonly pb::MessageParser<UInt64Value> _parser = new pb::MessageParser<UInt64Value>(() => new UInt64Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -610,10 +598,6 @@ public sealed partial class UInt64Value : pb::IMessage<UInt64Value>, pb::IMessag
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -621,7 +605,7 @@ public sealed partial class UInt64Value : pb::IMessage<UInt64Value>, pb::IMessag
   ///
   /// The JSON representation for `Int32Value` is JSON number.
   /// </summary>
-  public sealed partial class Int32Value : pb::IMessage<Int32Value>, pb::IMessage2 {
+  public sealed partial class Int32Value : pb::IMessage<Int32Value> {
     private static readonly pb::MessageParser<Int32Value> _parser = new pb::MessageParser<Int32Value>(() => new Int32Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -751,10 +735,6 @@ public sealed partial class Int32Value : pb::IMessage<Int32Value>, pb::IMessage2
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -762,7 +742,7 @@ public sealed partial class Int32Value : pb::IMessage<Int32Value>, pb::IMessage2
   ///
   /// The JSON representation for `UInt32Value` is JSON number.
   /// </summary>
-  public sealed partial class UInt32Value : pb::IMessage<UInt32Value>, pb::IMessage2 {
+  public sealed partial class UInt32Value : pb::IMessage<UInt32Value> {
     private static readonly pb::MessageParser<UInt32Value> _parser = new pb::MessageParser<UInt32Value>(() => new UInt32Value());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -892,10 +872,6 @@ public sealed partial class UInt32Value : pb::IMessage<UInt32Value>, pb::IMessag
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -903,7 +879,7 @@ public sealed partial class UInt32Value : pb::IMessage<UInt32Value>, pb::IMessag
   ///
   /// The JSON representation for `BoolValue` is JSON `true` and `false`.
   /// </summary>
-  public sealed partial class BoolValue : pb::IMessage<BoolValue>, pb::IMessage2 {
+  public sealed partial class BoolValue : pb::IMessage<BoolValue> {
     private static readonly pb::MessageParser<BoolValue> _parser = new pb::MessageParser<BoolValue>(() => new BoolValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1033,10 +1009,6 @@ public sealed partial class BoolValue : pb::IMessage<BoolValue>, pb::IMessage2 {
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -1044,7 +1016,7 @@ public sealed partial class BoolValue : pb::IMessage<BoolValue>, pb::IMessage2 {
   ///
   /// The JSON representation for `StringValue` is JSON string.
   /// </summary>
-  public sealed partial class StringValue : pb::IMessage<StringValue>, pb::IMessage2 {
+  public sealed partial class StringValue : pb::IMessage<StringValue> {
     private static readonly pb::MessageParser<StringValue> _parser = new pb::MessageParser<StringValue>(() => new StringValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1174,10 +1146,6 @@ public sealed partial class StringValue : pb::IMessage<StringValue>, pb::IMessag
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   /// <summary>
@@ -1185,7 +1153,7 @@ public sealed partial class StringValue : pb::IMessage<StringValue>, pb::IMessag
   ///
   /// The JSON representation for `BytesValue` is JSON string.
   /// </summary>
-  public sealed partial class BytesValue : pb::IMessage<BytesValue>, pb::IMessage2 {
+  public sealed partial class BytesValue : pb::IMessage<BytesValue> {
     private static readonly pb::MessageParser<BytesValue> _parser = new pb::MessageParser<BytesValue>(() => new BytesValue());
     private pb::UnknownFieldSet _unknownFields;
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
@@ -1315,10 +1283,6 @@ public sealed partial class BytesValue : pb::IMessage<BytesValue>, pb::IMessage2
       }
     }
 
-    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
-    public bool IsInitialized() {
-      return true;
-    }
   }
 
   #endregion