ServiceKnownTypeAttribute Class
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ServiceKnownTypeAttribute Class

Specifies known types to be used by a service when serializing or deserializing.

Namespace:  System.ServiceModel
Assembly:  System.ServiceModel (in System.ServiceModel.dll)

<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Method Or AttributeTargets.Interface, Inherited := True,  _
	AllowMultiple := True)> _
Public NotInheritable Class ServiceKnownTypeAttribute _
	Inherits Attribute
Dim instance As ServiceKnownTypeAttribute

The ServiceKnownTypeAttribute is intended for use when creating Windows Communication Foundation (WCF) service contracts (interfaces that define the service and its methods). The known types are types that may be present in an object graph when serialization or deserialization occurs. For more information about known types, see Data Contract Known Types.

To use the MethodName property, create a class that contains a method (or methods) that returns an array of types (each being a known type). When applying the attribute, set the methodName to the name of a method that returns the list of types and set the declaringType to the type that contains the method. The method must return a type that implements the IEnumerable(Of T) interface. The method must also include a parameter of type ICustomAttributeProvider.

You can also apply the attribute several times to an interface, class, or method, each time specifying a new known type.


You can use the word ServiceKnownType in your Microsoft Visual Basic or C# code instead of the longer ServiceKnownTypeAttribute.

The following example applies the ServiceKnownTypeAttribute attribute to an interface where the attribute specifies a method name and a declaring type.

' Define a service contract and apply the ServiceKnownTypeAttribute 
' to specify types to include when generating client code.  
' The types must have the DataContractAttribute and DataMemberAttribute 
' applied to be serialized and deserialized. The attribute specifies the  
' name of a method (GetKnownTypes) in a class (Helper) defined below.
<ServiceKnownType("GetKnownTypes", GetType(Helper)), ServiceContract()>  _
Public Interface ICalculator
    ' Any object type can be inserted into a Hashtable. The  
    ' ServiceKnownTypeAttribute allows you to include those types 
    ' with the client code.
    <OperationContract()>  _
    Function GetItems() As Hashtable 
End Interface  

' This class has the method named GetKnownTypes that returns a generic IEnumerable. 
Friend Class Helper
    Public Shared   Function GetKnownTypes(provider As ICustomAttributeProvider) _
     As IEnumerable(of Type) 
        Dim knownTypes As List(Of Type) = New List(Of Type)
        ' Add any types to include here.
        Return knownTypes
    End Function  
End Class 

<DataContract()>  _
Public Class Widget
    <DataMember()>  _
    Public Id As String
    <DataMember()>  _
    Public Catalog As String 
End Class 

<DataContract()>  _
Public Class Machine
    Inherits Widget
    <DataMember()>  _
    Public Maker As String 
End Class

Alternatively, apply the attribute to the interface specifying the known type to include.

' Apply the ServiceKnownTypeAttribute to the  
' interface specifying the type to include. Apply the attribute 
' more than once, if needed.
<ServiceKnownType(GetType(Widget)), ServiceKnownType(GetType(Machine)), _
 ServiceContract()>  _
Public Interface ICalculator2
    ' Any object type can be inserted into a Hashtable. The  
    ' ServiceKnownTypeAttribute allows you to include those types 
    ' with the client code.
    <OperationContract()>  _
    Function GetItems() As Hashtable 
End Interface


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0

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