' Implement the IExtensibleDataObject interface 
' to store the extra data for future versions.
<DataContract(Name := "Person", [Namespace] := "http://www.cohowinery.com/employees")>  _
Class Person
    Implements IExtensibleDataObject
    ' To implement the IExtensibleDataObject interface,
    ' you must implement the ExtensionData property. The property
    ' holds data from future versions of the class for backward
    ' compatibility.
    Private extensionDataObject_value As ExtensionDataObject

    Public Property ExtensionData() As ExtensionDataObject _
       Implements IExtensibleDataObject.ExtensionData
        Get
            Return extensionDataObject_value
        End Get
        Set
            extensionDataObject_value = value
        End Set
    End Property
    <DataMember()>  _
    Public Name As String
End Class 

' The second version of the class adds a new field. The field's 
' data is stored in the ExtensionDataObject field of
' the first version (Person). You must also set the Name property 
' of the DataContractAttribute to match the first version. 
' If necessary, also set the Namespace property so that the 
' name of the contracts is the same.

<DataContract(Name := "Person", [Namespace] := "http://www.cohowinery.com/employees")>  _
Class PersonVersion2
    Implements IExtensibleDataObject

    ' Best practice: add an Order number to new members.
    <DataMember(Order:=2)>  _
    Public ID As Integer

    <DataMember()>  _
    Public Name As String

    Private extensionDataObject_value As ExtensionDataObject

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

// Implement the IExtensibleDataObject interface 
// to store the extra data for future versions.
[DataContract(
    Name = "Person",
    Namespace = "http://www.cohowinery.com/employees")]
class Person : IExtensibleDataObject
{
    // To implement the IExtensibleDataObject interface,
    // you must implement the ExtensionData property. The property
    // holds data from future versions of the class for backward
    // compatibility.
    private ExtensionDataObject extensionDataObject_value;
    public ExtensionDataObject ExtensionData
    {
        get
        {
            return extensionDataObject_value;
        }
        set
        {
            extensionDataObject_value = value;
        }
    }
    [DataMember]
    public string Name;
}

// The second version of the class adds a new field. The field's 
// data is stored in the ExtensionDataObject field of
// the first version (Person). You must also set the Name property 
// of the DataContractAttribute to match the first version. 
// If necessary, also set the Namespace property so that the 
// name of the contracts is the same.
[DataContract(Name = "Person",
    Namespace = "http://www.cohowinery.com/employees")]
class PersonVersion2 : IExtensibleDataObject
{
    // Best practice: add an Order number to new members.
    [DataMember(Order=2)]
    public int ID;

    [DataMember]
    public string Name;

    private ExtensionDataObject extensionDataObject_value;
    public ExtensionDataObject ExtensionData
    {
        get
        {
            return extensionDataObject_value;
        }
        set
        {
            extensionDataObject_value = value;
        }
    }
}