Properties-of-XmlNode

Properties of XML nodes

Adapted properties may conflict with native

PowerShell provides an adapter for XmlNode and derived classes. As a result, we can use the dot-notation in order to access XmlElement attributes and child nodes as if they were properties. This is very handy. But adapted properties may hide native .NET properties.

All native properties are potentially troublesome. The property Name is very likely troublesome because this name is often used for element attributes.

Thus, the expression $elem.Name is ambiguous. It gets the element name if an attribute "Name" or child elements "Name" are not present and gets their values otherwise. Note that adapted properties are case insensitive, so that "name" and "NAME" nodes also hide the element property Name with dot-notation.

A reliable way to get an element name is

$elem.get_Name()

A reliable and case sensitive way to get an attribute "Name" value is

$elem.GetAttribute('Name')

Scripts

• Test-1.Element.ps1 - .Name gets element name
• Test-2.Attribute.ps1 - .Name gets value of attribute name
• Test-3.ChildNode.ps1 - .Name gets value of child element name

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Adapted properties accept only string values

Fixed in v6

In many cases PowerShell converts values to required target types. PowerShell refuses to convert not string values to strings on setting adapted properties of XmlNode. This may be unexpected, some code may work for a while with string values, and fail later when not strings are assigned.

The script Test-4.Cannot.set.number.ps1 shows the issue.

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Adapted properties have different nature

An adapted property may represent

1. A single attribute value (String), read/write.
2. A single element text (String), read/write.
3. Several objects (Object[]), read only.

As a result, if XML structure is not known for sure then use of adapted node properties may cause mistakes. Some unexpected values may be returned or set.

The script Test-5.Cannot.set.string.ps1 shows the above cases.