Question : Raising events with asynchronous callback from a dll

This is a VB.Net Question
OK, so I've figured (with some help) out how to receive an asynchronous callback from a dll written in C++ using delegates.  But I've also just figured out that a) callbacks run on separate threads from the UI and b) I don't -need/want- a separate thread.  What I'd like to do is have the callback raise an event that interrupts rather than 'parallel' (a separate thread) the main thread (if possible).
So this is a three part question:
1)  Is it possible to for a callback to raise an event in the primary thread?
2) If this isn't possible, is there any way to use events for this purpose or should I simply resign myself to handling a separate thread for each callbacks?
3) Any code examples of how to do either would be great, thanks
pgb

Answer : Raising events with asynchronous callback from a dll

Invoke or BeginInvoke functions can help you to call form functions from callback.
For example:

Delegate Sub CallbackDelegate(ByVal n1 As Integer, ByVal n2 As Integer)

Public Class MainForm Inherits System.Windows.Forms.Form

        ' this is callback running in the context of caller thread
        Private Sub CallbackFunction(ByVal n1 As Integer, ByVal n2 As Integer)
              Me.BeginInvoke( _
                  New  CallbackDelegate(AddressOf Me.HandleData), _
                  New Object() {n1, n2})
        End Sub

        ' This function runs in the main application thread and called indirectly from CallbackFunction
        Private Sub HandleData(ByVal n1 As Integer, ByVal n2 As Integer)
             ...
        End Sub

        ...

End Class