DataMemberAttribute.EmitDefaultValue 屬性

定義

命名空間:

System.Runtime.Serialization

組件:

System.Runtime.Serialization.Primitives.dll

來源:

DataMemberAttribute.cs

取得或設定值，這個值會指定即將序列化之欄位或屬性的預設值是否要加以序列化。

public:
 property bool EmitDefaultValue { bool get(); void set(bool value); };

public bool EmitDefaultValue { get; set; }

member this.EmitDefaultValue : bool with get, set

Public Property EmitDefaultValue As Boolean

屬性值

Boolean

如果應該要在序列化資料流中產生成員的預設值，則為 true，否則為 false。 預設為 true。

範例

下列程式碼範例會示範在各種欄位上將 EmitDefaultValue 屬性設定為 false。

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

    // This will be written as <employeeID>0</employeeID>
    [DataMember]
    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;
}

<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

備註

在 .NET Framework 中，類型內含有預設值的概念。 例如，對於任何參考型別，預設值為 null ，而整數類型則為 0。 有時候，當資料成員設為預設值時，會需要從序列化資料中省略該資料成員。 若要這麼做，請將 EmitDefaultValue 屬性設定為 false (預設值為 true)。

注意

我們建議不要將 EmitDefaultValue 屬性設定為 false。 您應該只在特定需求時才這樣處理 (例如，為了提供互通性或是縮減資料大小)。