Assembly: System.Xml (in System.Xml.dll)
The XML schema specification for structures allows an XML document to explicitly signal that an element's content is missing. Such an element contains the attribute xsi:nil set to true. For more information, see the World Wide Web Consortium (www.w3.org) specification, XML Schema Part 1: Structures.
If the property is true, the xsi:nil attribute is generated for class members that have been set to null. For example, if you set a field named MyStringArray to null, the XmlSerializer generates the following XML code.
<MyStringArray xsi:nil = "true" />
If the property is false, no XML element is generated.
You cannot apply the property to a member typed as a value type because a value type cannot contain null.