KnownTypeAttribute Class
Specifies types that should be recognized by the DataContractSerializer when serializing or deserializing a given type.
Assembly: System.Runtime.Serialization (in System.Runtime.Serialization.dll)
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.
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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
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.
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