dotnet-fixedwidth

A simple library to assist with parsing fixed-width data (files) in .NET Core (C#)

Usage:

Create one or more classes implementing IFixedWidthInputRecordDefinition (defines the shape of the fixed-width line & how to parse):

public class TestInputRecordDefinition : IFixedWidthInputRecordDefinition
        {
            public string RecordName
            {
                get { return "TestRecord"; }
            }

            public IList<FixedWidthInputFieldDefinition> FieldDefinitions
            {
                get {
                    return new[] {
                        FixedWidthInputFieldDefinition.Create("NameField", 20, x => x.Trim()),
                        FixedWidthInputFieldDefinition.Create("FamilySizeField", 2, FixedWidthParser.ParseInt),
                        FixedWidthInputFieldDefinition.Create("BirthdayField", 10, FixedWidthParser.ParseIso8601Date)
                    };
                }
            }
        }

Define one or more types for output records (no specific base class is necessary) with public properties decorated with FixedWidthField

public class TestOutputRecord
{
    [FixedWidthField("TestRecord", "NameField")]
    public string Name { get; set; }

    [FixedWidthField("TestRecord", "FamilySizeField")]
    public int NumberOfPeopleInFamily { get; set; }

    [FixedWidthField("TestRecord", "BirthdayField")]
    public DateTime Birthday { get; set; }
}

Note that the first parameter of the FixedWidthField corresponds to IFixedWidthInputRecordDefinition::RecordName.

Instantiate the parser:

var parser = new FixedWidthParser<TestOutputRecord>(new TestInputRecordDefinition());

Parse:

IEnumerable<string> inputLines = ...

foreach (var record in parser.Parse(inputLines)) {
    Console.Out.WriteLine(record.Birthday.DayOfWeek);
}

There is an alternative method ParseIter which returns IEnumerator<TResultRecord> as well as a static method DumpRecord(IFixedWidthInputRecordDefinition recordDefinition, string line) which can assist debugging (e.g. when defining IFixedWidthInputRecordDefinition