Sendmessage from VB6 to vb.NET problem

[Elgerm]

I'm trying to send a windows message from vb6 to a vb.net app. The problem is that I can recieve a message, but the string I send with it is not recieved correctly by the vb.net app. When I try to put it back into a string again I get garbage.

Here is some code from the sending app (vb6):

Private Sub cmdSendData_Click()
Dim sString As String
Dim lHwnd   As Long
Dim cds     As COPYDATASTRUCT
Dim buf(1 To 255) As Byte

sString = Trim$(txtString)
If sString = "" Then Exit Sub
'
' Get the handle of the target application's visible window.
'
lHwnd = FindWindow(vbNullString, cWINDOW_TITLE)
'
' Copy the string into a byte array,
' converting it to ASCII. Assign lpData
' the address of the byte array.
'
Call CopyMemory(buf(1), ByVal sString, Len(sString))
With cds
    .dwData = 3
    .cbData = Len(sString) + 1
    .lpData = VarPtr(buf(1))
End With
'
' Send the string.
'
Call SendMessage(lHwnd, WM_COPYDATA, Me.hwnd, cds)
End Sub

And here is the recieving app(vb.net):

  Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
    If m.Msg = MainForm.WM_COPYDATA Then
      Dim data As CopyData
      Dim message As String

      ' get the data...
      data = CType(m.GetLParam(GetType(CopyData)), CopyData)
      message = Marshal.PtrToStringAuto(data.lpData, data.cbData \ Marshal.SystemDefaultCharSize)

      ' add the message
      Messages.Items.Add(String.Format("{0}: {1}", DateTime.Now.ToShortTimeString(), message))

      ' let them know we processed the message...
      m.Result = New IntPtr(1)
    Else
      MyBase.WndProc(m)
    End If
  End Sub

  Private Const WM_COPYDATA As Integer = &H4A

  <StructLayout(LayoutKind.Sequential)> _
  Private Structure CopyData
    Public dwData As IntPtr
    Public cbData As Integer
    Public lpData As IntPtr
  End Structure

If I send the same message from a vb.net app then everything works.
Can anyone tell me what I'm doing wrong?

Thanks!

 

[Elgerm]

ok fixed it!

changes (in the .net code):

'message = Marshal.PtrToStringAuto(data.lpData, data.cbData \   Marshal.SystemDefaultCharSize)
Dim B(255) As Byte
Marshal.Copy(data.lpData, B, 0, 255)
message = System.Text.Encoding.Default.GetString(B)

this is really handy when you're stuck with old vb6 apps and you're slowly migrating to vb.net.