XmlRootAttribute.IsNullable Property

Definition

Gets or sets a value that indicates whether the XmlSerializer must serialize a member that is set to null into the xsi:nil attribute set to true.

public bool IsNullable { get; set; }

Property Value

true if the XmlSerializer generates the xsi:nil attribute; otherwise, false.

Examples

The following example serializes a class named Group. The example applies the XmlRootAttribute to the class, and sets the IsNullable property to false.

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

// Apply the XmlRootAttribute and set the IsNullable property to false.
[XmlRoot(IsNullable = false)]
public class Group
{
   public string Name;
}

public class Run
{
   public static void Main()
   {
   Console.WriteLine("Running");
      Run test = new Run();
      test.SerializeObject("NullDoc.xml");
   }

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

      // Writing the file requires a TextWriter.
      TextWriter writer = new StreamWriter(filename);

      // Create the object to serialize.
      Group mygroup = null;

      // Serialize the object, and close the TextWriter.
      s.Serialize(writer, mygroup);
      writer.Close();
   }
}

Remarks

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 XML Schema Part 1: Structures Second Edition.

If the IsNullable property is set to true, the xsi:nil attribute is generated as shown in the following XML:

<?xml version="1.0" encoding="utf-8"?>  
<Group xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xsi:nil="true" />  

If the IsNullable property is false, an empty element is created as shown in the following code:

<?xml version="1.0" encoding="utf-8"?>  
<Group xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
xmlns:xsd="http://www.w3.org/2001/XMLSchema" />  

Applies to

Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1
UWP 10.0