CSLA as well as well as the proxy architecture I created for my last project, utilize serialization of objects to be passed across the wire, and deserialized on the other side into the same type of object.

This is different from passing datasets, which are then read into business objects.  We are actually passing the serialized version of the business object.

So what happens if you make a change to a business object such as adding a public property.  Will clients who have the old version of the Business Object be forced to upgrade? 

To see the answers along with some sample code for testing this out click on the link to read the full article.

So lets say you have a class that exposes 20 properties and 40 methods.  This business object is deployed on hundreds of clients computers.  When they send the BizObject over the wire, it is deserialized back into the exact same object on the server. 

But now, for whatever reason, you need to add 1 property to this BizObject.  For the current set of clients using this business object, you don’t really need to deploy the updated change unless you have to in order to keep it from breaking.

So do you need to redeploy?  Probably not.

I serialzied a business object into a base64 encoded string and then added a public property to the object and tried to deserialize it with the “old” serialized string.  The result?  It worked.  The properties that had values when I first serialized it kept their values.  The fact that there were new properties didn’t cause a problem.

How about going the other way: removing a public property that had a value when it was serialized, but doesn’t exist with deserialized.  Again, this works. 

When doesn’t it work?  When you are trying to deserialze into a different class, or a different namespace for the same class. 

So you can’t serialize classA and deserialize it into classB, even if both expose the exact same signature.  The same goes for namespaces.  If you serialize classA, and then change it’s namespace and try to deserialize it, you will get an exception.

You can try it out with the following code:

Imports WindowsApplication1.ASDF


Public Class Form1

    Private Sub toString_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdToString.Click
        Dim o As New A
        o.A11 = "this is a test"
        o.Asdf1 = "another test"

        Me.TextBox2.Text = EncodeBase64(o.CloneString)
        MsgBox(EncodeBase64(o.CloneString))
    End Sub

    Private Sub fromString_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles fromString.Click
        Dim o As A = A.Hydrate(DecodeBase64(Me.TextBox1.Text))
        MsgBox(o.A11)
        MsgBox(o.Asdf1)
        MsgBox(o.asdfdsa)
    End Sub

    Public Function EncodeBase64(ByVal input As String) As String
        Dim strBytes() As Byte = System.Text.Encoding.UTF8.GetBytes(input)
        Return System.Convert.ToBase64String(strBytes)
    End Function

    Public Function DecodeBase64(ByVal input As String) As String
        Return System.Text.Encoding.UTF8.GetString(System.Convert.FromBase64String(input))
    End Function

End Class


<Serializable()> _
Public Class Parent

    Public Function CloneString() As String
        Dim bFormatter As New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
        Dim stream As New System.IO.MemoryStream()
        bFormatter.Serialize(stream, Me)
        stream.Flush()
        stream.Position = 0
        Dim bytes() As Byte = stream.ToArray()

        Return System.Text.Encoding.Default.GetString(bytes)
    End Function

    Public Shared Function StringToStream(ByVal str As String) As System.IO.Stream
        Return New System.IO.MemoryStream(System.Text.Encoding.Default.GetBytes(str))
    End Function

End Class

<Serializable()> _
Public Class A
    Inherits Parent

    Private a1 As String
    Private asdf As String
    Public Property A11() As String
        Get
            Return a1
        End Get
        Set(ByVal value As String)
            a1 = value
        End Set
    End Property

    Public Property Asdf1() As String
        Get
            Return asdf
        End Get
        Set(ByVal value As String)
            asdf = value
        End Set
    End Property
    Public Function asdfdsa() As String
        Return "Asdf"
    End Function
    Public Shared Function Hydrate(ByVal s As String) As A
        Dim bFormatter As New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
        Dim stream2 As System.IO.MemoryStream = StringToStream(s)
        stream2.Flush()
        stream2.Position = 0
        Dim newClone As A
        newClone = CType(bFormatter.Deserialize(stream2), A)
        Return newClone
    End Function

End Class