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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 (www.w3.org) 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.

NoteNote:

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();
      test.SerializeObject("TypeDoc.xml");
   }

   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);
      writer.Close();

   }
}
#using <mscorlib.dll>
#using <System.Xml.dll>
#using <System.dll>
using namespace System;
using namespace System::IO;
using namespace System::Xml::Serialization;

public __gc class Employee
{
public:
   String* Name;
};

public __gc class Manager:public Employee
{
public:
   int Level;
};

public __gc class Group
{   
public:
   [XmlArray(IsNullable = true)]
   [XmlArrayItem(__typeof(Manager), IsNullable = false),
      XmlArrayItem(__typeof(Employee), IsNullable = false)]
   Employee* Employees[];
};   

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 = 0;

   // Creates a null Employee object.
   Employee* y = 0;

   Employee* temp[] = {mgr, y};      
   group->Employees = temp;

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

}

int main()
{
   SerializeObject(S"TypeDoc.xml");
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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