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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 Property EmitDefaultValue As Boolean

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 Nothing, 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.

<DataContract()>  _
Public Class Employee
    ' The CLR default for as string is a null value. 
    ' This will be written as <employeeName xsi:nil="true" />
    <DataMember()>  _
    Public employeeName As String = Nothing 

    ' This will be written as <employeeID>0</employeeID>
    <DataMember()>  _
    Public employeeID As Integer = 0

    ' The next two will not be written because the EmitDefaultValue = false.
    <DataMember(EmitDefaultValue := False)> Public position As String = Nothing
    <DataMember(EmitDefaultValue := False)> Public salary As Integer = 0

    ' This will be written as <targetSalary>555</targetSalary> because  
    ' the 555 does not match the .NET default of 0.
    <DataMember(EmitDefaultValue := False)> Public targetSalary As Integer = 555
End Class

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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