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 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.

<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 

Universal Windows Platform
Available since 8
.NET Framework
Available since 3.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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