When you call this function, the WndProc function must respond to the WM_NCCREATE message by returning TRUE. If it does not, the creation process will fail. A null handle will be returned from CreateWindowEx and GetLastError will return 0. See MSDN on WM_NCCREATE (http://msdn.microsoft.com/en-us/library/ms632635.aspx) and also WM_CREATE (http://msdn.microsoft.com/en-us/library/ms632619.aspx). You can have your WndProc call DefWindowProc, which will take care of this issue.

            wndclass.lpfnWndProc = (WndProc)((hWnd, message, wParam, lParam ) => {

     GWL_WNDPROC =    (-4),

     GWL_WNDPROC = -4

     GWL_WNDPROC =    (-4),

     GWL_WNDPROC = -4

        Public lpfnWndProc As IntPtr

        .lpfnWndProc = IntPtr.Zero

    base.WndProc (ref m);

Use the version that takes a delegate as last parameter if you don't explicitly handle the WM_TIMER message or if you don't override WndProc. In that case DefWndProc will invoke your callback when the time-out value elapses.

///         <term>WH_CALLWNDPROC (4)</term>

///         destination window procedure. For more information, see the CallWndProc hook procedure.

///         <term>WH_CALLWNDPROC (4)</term>

    Public lpfnWndProc As IntPtr

    .lpfnWndProc = IntPtr.Zero

// Override the WndProc function in the form

' Override the WndProc function which is called when the play function ends

Things like RegisterWindowClass and GetClassInfo using the WNDCLASS structure in different ways requires creating separate structures with different field types in order to satisfy the marshaller (The WndProc pointer as a raw IntPtr in some cases, or as a method pointer in other cases). I can see that the params for GetClassInfo and RegisterWindowClass do take different structure types, but those types do not appear to be documented here.

     GCLP_WNDPROC       = -24,

     GCLP_WNDPROC       = -24

     GCLP_WNDPROC       As Long = -24

     WH_CALLWNDPROC = 4,

     WH_CALLWNDPROC = 4

     GWL_WNDPROC = -4,

     GWL_WNDPROC = -4

     GWL_WNDPROC As Long = -4

delegate IntPtr WndProc (IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

Delegate Function WndProc (ByVal hWnd As IntPtr, ByVal msg As Integer, _

Check with WindowsMessages for a list of most (if not all) of the constants that will be passed in as messages to the WndProc method.

   public WndProc lpfnWndProc;

   Public lpfnWndProc As WndProc

   Public lpfnWndProc As IntPtr

static readonly int GWL_WNDPROC    = -4;

Public Const GWL_WNDPROC    = -4

     GWL_WNDPROC = -4,