Hi Mattias,

i solved it another way, but my problem is passing
the data between two windows does not work. I get
garbage at the other end when passing the data with
the WM_COPYDATA Message.

Here is Code:

//structure to pass
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct APP_IP_GUID_INFORMATION
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
public string ApplicationGUID;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
public string IPAddress;
}

[StructLayout(LayoutKind.Sequential)]
public struct CopyDataStruct
{
public int dwData;
public int cbData;
public IntPtr pData;
}

IntPtr ptrAIGI = IntPtr.Zero;
IntPtr ptrCDS = IntPtr.Zero;
IntPtr hWnd = IntPtr.Zero;

GGIPAWin32APIClass.APP_IP_GUID_INFORMATION aigi;
aigi.ApplicationGUID = this.guidApplicationGUID.ToString();
aigi.IPAddress = this.textBoxGGIPAIPAddress.Text;

ptrAIGI =
Marshal.AllocHGlobal(Marshal.SizeOf(typeof(GGIPAWin32APIClass.APP_IP_GUID_INFORMATION)));
Marshal.StructureToPtr(aigi, ptrAIGI, false);

GGIPAWin32APIClass.CopyDataStruct cds;
cds.dwData = this.Handle.ToInt32();
cds.cbData =
Marshal.SizeOf(typeof(GGIPAWin32APIClass.APP_IP_GUID_INFORMATION));
cds.pData = ptrAIGI;

ptrCDS =
Marshal.AllocHGlobal(Marshal.SizeOf(typeof(GGIPAWin32APIClass.CopyDataStruct)));
Marshal.StructureToPtr(cds, ptrCDS, false);

/*...........*/

hWnd = new IntPtr(Convert.ToInt32(ClienthWnd.Key.ToString()));
HandleRef hWndRef = new HandleRef(this,hWnd);
GGIPAWin32APIClass.SendMessage(hWndRef,
(uint)GGIPAWin32APIClass.WindowsMessages.WM_COPYDATA, this.Handle, ptrCDS)

/*...........*/

Marshal.FreeHGlobal(ptrAIGI);
Marshal.FreeHGlobal(ptrCDS);

The dwData and cbData at the other end are ok, but the pointer to the data
is garbage,...why.
Any idea? All pinvoke-functions and data is ASCII or ANSI,...

Thanks in advance,...

Regards

Kerem