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XmlArrayItemAttribute.IsNullable Property

Gets or sets a value that indicates whether the XmlSerializer must serialize a member as an empty XML tag with the xsi:nil attribute set to true.

Namespace:  System.Xml.Serialization
Assembly:  System.Xml (in System.Xml.dll)

public bool IsNullable { get; set; }

Property Value

Type: System.Boolean
true if the XmlSerializer generates the xsi:nil attribute; otherwise, false, and no instance is generated. The default is true.

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 ( specification titled "XML Schema Part 1: Structures."

If the IsNullable 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 IsNullable property is false, no XML element is generated.


You cannot apply the IsNullable property to a member typed as a value type because a value type cannot contain null.

The following example serializes a class named Group, which contains a field named Employees that returns an array of Employee objects. A second class named Manager derives from Employee. An XmlArrayItemAttribute specifies that the XmlSerializer can insert both Employee and Manager objects into the array. The example sets the IsNullable property, thereby telling the XmlSerializer not to generate the xsi:nil attribute objects in the array set to null.

using System;
using System.IO;
using System.Xml.Serialization;

public class Group
   [XmlArray(IsNullable = true)]
   [XmlArrayItem(typeof(Manager), IsNullable = false),
   XmlArrayItem(typeof(Employee), IsNullable = false)]
   public Employee[] Employees;

public class Employee
   public string Name;

public class Manager:Employee
   public int Level;

public class Run
   public static void Main()
      Run test = new Run();

   public void SerializeObject(string filename)
      XmlSerializer s = new XmlSerializer(typeof(Group));

      // To write the file, a TextWriter is required.
      TextWriter writer = new StreamWriter(filename);

      // Creates the object to serialize.
      Group group = new Group();

      // Creates a null Manager object.
      Manager mgr = null;

      // Creates a null Employee object.
      Employee y = null;

      group.Employees = new Employee[2] {mgr, y};

      // Serializes the object and closes the TextWriter.
      s.Serialize(writer, group);


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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