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DataMemberAttribute.EmitDefaultValue Property

Gets or sets a value that specifies whether to serialize the default value for a field or property being serialized.

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

public bool EmitDefaultValue { get; set; }

Property Value

Type: System.Boolean
true if the default value for a member should be generated in the serialization stream; otherwise, false. The default is true.

In the .NET Framework, types have a concept of default values. For example, for any reference type the default value is null, and for an integer type it is 0. It is occasionally desirable to omit a data member from the serialized data when it is set to its default value. To do this, set the EmitDefaultValue property to false (it is true by default).


Setting the EmitDefaultValue property to false is not a recommended practice. It should only be done if there is a specific need to do so (such as for interoperability or to reduce data size).

The following example shows the EmitDefaultValue property set to false on various fields.

public class Employee
    // The CLR default for as string is a null value.
    // This will be written as <employeeName xsi:nill="true" />
    public string EmployeeName = null;

    // This will be written as <employeeID>0</employeeID>
    public int employeeID = 0;

    // The next three will not be written because the EmitDefaultValue = false.
    [DataMember(EmitDefaultValue = false)]
    public string position = null;
    [DataMember(EmitDefaultValue = false)]
    public int salary = 0;
    [DataMember(EmitDefaultValue = false)]
    public int? bonus = null;

    // This will be written as <targetSalary>57800</targetSalary> 
    [DataMember(EmitDefaultValue = false)]
    public int targetSalary = 57800;

.NET Framework

Supported in: 4, 3.5, 3.0

.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 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.