VB.NET serialization error

Question

I'm trying to serialize the main class in my VB solution. I've added the Serializable attribute at the top of my class like so:

<Serializable()>
Public Class Form1

and I'm using the following code to serialize:

Public Sub serializeThis()
    Dim fStream As FileStream
    Try
        fStream = New FileStream("C:\ObjectData.bin", FileMode.Create)
        Dim bfmtr As New BinaryFormatter
        bfmtr.Serialize(fStream, Me)
        fStream.Close()
    Catch ex As Exception
        MsgBox("Failed to serialize: " & ex.Message)
        Throw
    End Try
End Sub

When I call this method I'm getting the error:

Type 'System.Windows.Forms.Form' in Assembly 'System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable.

I'm guessing this is because you can't serialize the form that is attached to the class or something, but I really don't know what I'm doing.

Can I serialize all of the objects contained in my Form1 class somehow, without getting this error? I don't want to store any data about the form controls, I just need to save all the objects that I've defined at the top of the Form1 class.

Thanks for any help.

score 4 · Accepted Answer · answered Apr 05 '11 at 08:39

Since Form is not serializable, you cannot serialize the form itself. (The form is not attached to your Form1 class. Your Form1 class is the form, since it derives from System.Windows.Forms.Form.)

What you can do, however, is to serialize just the objects you want to serialize:

Public Sub SerializeThis()
    Dim fStream As FileStream
    Try
        fStream = New FileStream("C:\ObjectData.bin", FileMode.Create)
        Dim bfmtr As New BinaryFormatter()

        bfmtr.Serialize(fStream, object1)
        bfmtr.Serialize(fStream, object2)
        bfmtr.Serialize(fStream, object3)
        ' ...

        fStream.Close()
    Catch ex As Exception
        MsgBox("Failed to serialize: " & ex.Message)
        Throw
    End Try
End Sub

There are two things to watch out for:

The classes of all the objects you want to serialize (object1, object2, ...) must be marked as <Serializable()>. You can check this in the documentation (Example: Hashtable is marked as serializable).
Be sure to deserialize the objects in the same order.

Thanks, that explains the error. The problem is that I've got quite a large number of these objects in the Form1 class (all serializable as far as I know) and I was hoping to avoid explicitly serializing each one. If I move the objects I want to persist to a separate class, would that work? Otherwise, can you possibly explain why I need to deserialize in the same order? Cheers — Flash, Apr 05 '11 at 09:28
@Andrew: Yes, putting them in a separate class should work. You need to mark this class as ``. It's good practice to separate user interface (Form1) and data (your new class) anyway. — Heinzi, Apr 05 '11 at 11:22
@Andrew: You need to deserialize them in the same order, because your file stream will contain `bytesForObject1 bytesForObject2 ...`, and reconstructing an object2 out of `bytesForObject1` won't work. ;-) — Heinzi, Apr 05 '11 at 11:23

VB.NET serialization error

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