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KnownTypeAttribute Class

Specifies types that should be recognized by the DataContractSerializer when serializing or deserializing a given type.

System.Object
  System.Attribute
    System.Runtime.Serialization.KnownTypeAttribute

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

'Declaration
<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Struct, Inherited := True,  _
	AllowMultiple := True)> _
Public NotInheritable Class KnownTypeAttribute _
	Inherits Attribute

The KnownTypeAttribute type exposes the following members.

  NameDescription
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsKnownTypeAttribute(String)Initializes a new instance of the KnownTypeAttribute class with the name of a method that returns an IEnumerable of known types.
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsKnownTypeAttribute(Type)Initializes a new instance of the KnownTypeAttribute class with the specified type.
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  NameDescription
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsMethodNameGets the name of a method that will return a list of types that should be recognized during serialization or deserialization.
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsTypeGets the type that should be recognized during serialization or deserialization by the DataContractSerializer.
Public propertyTypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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  NameDescription
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeWhen overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)
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Apply the KnownTypeAttribute attribute to a type to indicate to the DataContractSerializer types that should be recognized when serializing or deserializing an instance of the type to which the attribute is applied. This attribute could also be recognized by other serializers that understand data contracts.

NoteNote

In your code, you can use the word KnownType instead of the longer KnownTypeAttribute.

You can either apply exactly one KnownTypeAttribute instance with the MethodName property set, or one or more KnownTypeAttribute instances with the Type property set.

The following example shows a type named Person and a type named IDInformation that should be recognized when serializing or deserializing the Person type.

Imports System
Imports System.Collections.Generic
Imports System.Collections
Imports System.Text
Imports System.IO
Imports System.Runtime.Serialization
Imports System.Xml

Class Program

    Shared Sub Main(ByVal args() As String)
        Try
            Serialize("KnownTypeAttributeExample.xml")
            Deserialize("KnownTypeAttributeExample.xml")
            ' Run this twice. The second time, comment out the 
            ' Serialize call and comment out the  
            ' KnownTypeAttribute on the Person class. The 
            ' deserialization will then fail. 
        Catch exc As SerializationException
            Console.WriteLine("{0}: {1}", exc.Message, exc.StackTrace)
        Finally
            Console.WriteLine("Press Enter to exit...")
            Console.ReadLine()
        End Try 

    End Sub 


    Public Shared Sub Serialize(ByVal path As String)
        Dim p As New Person()
        p.Miscellaneous.Add(DateTime.Now, "Hello")
        p.Miscellaneous.Add(DateTime.Now.AddSeconds(1), "World")
        Dim w As New IDInformation()
        w.ID = "1111 00000"
        p.Miscellaneous.Add(DateTime.Now.AddSeconds(2), w)
        Dim ser As New DataContractserializer(GetType(Person))
        Using fs As New FileStream(path, FileMode.OpenOrCreate)
            ser.WriteObject(fs, p)
        End Using 
    End Sub 

    Public Shared Sub Deserialize(ByVal path As String)
        Dim ser As New DataContractserializer(GetType(Person))
        Using fs As New FileStream(path, FileMode.OpenOrCreate)
            Dim p2 As Person = ser.ReadObject(fs)
            Console.WriteLine("Count {0}", p2.Miscellaneous.Count)
            For Each de As DictionaryEntry In p2.Miscellaneous
                Console.WriteLine("Key {0} Value: {1}", de.Key, _
                de.Value)
                If TypeOf (de.Value) Is IDInformation Then 
                    Dim www As IDInformation = de.Value
                    Console.WriteLine( _
                    "Found ID Information. ID: {0}", www.ID)
                End If 
            Next 
        End Using 
    End Sub 

    ' Apply the KnownTypeAttribute to the class that  
    ' includes a member that returns a Hashtable.
    <System.Runtime.Serialization.KnownType(GetType(IDInformation))> _
    <DataContract()> _
    Public Class Person
        Implements IExtensibleDataObject
        Private MiscellaneousValue As New Hashtable()
        Private ExtensionDataObjectValue As ExtensionDataObject

        Public Property ExtensionData() As ExtensionDataObject _
            Implements IExtensibleDataObject.ExtensionData
            Get 
                Return ExtensionDataObjectValue
            End Get 
            Set(ByVal value As ExtensionDataObject)
                ExtensionDataObjectValue = value
            End Set 
        End Property

        <DataMember()> _
        Public Property Miscellaneous() As Hashtable
            Get 
                Return MiscellaneousValue
            End Get 
            Set(ByVal value As Hashtable)
                MiscellaneousValue = value
            End Set 
        End Property 
    End Class

    <DataContract()> _
    Public Class IDInformation
        Implements IExtensibleDataObject

        Private ExtensionDataObjectValue As ExtensionDataObject

        Public Property ExtensionData() As ExtensionDataObject _
            Implements IExtensibleDataObject.ExtensionData
            Get 
                Return ExtensionDataObjectValue
            End Get 

            Set(ByVal value As ExtensionDataObject)
                ExtensionDataObjectValue = value
            End Set 
        End Property

        <DataMember()> _
        Public ID As String 
    End Class 
End Class

.NET Framework

Supported in: 4.5.2, 4.5.1, 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

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

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.

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