Messages not reaching WndProc

[Kastro]

I am writing a class that overrides Control and utilizes the non-client area. I need to be able to have hotspots within the non-client area. However, because of what seems to me to be unusual behavior, I am not able to get it working. I override WndProc to intercept WM_NCMOUSEMOVE and WM_NCPAINT (as well as WM_NCCALCSIZE, WM_NCHITTEST, and WM_LBUTTONDOWN/UP) as follows: (Please don't flame me for posting VB.NET code. I use both interchangably as they are pretty much the same thing anyways. It just so happens that I wrote this in VB.NET. I posted here because I would guess that C# programmers know more about the Win32 API than VB.NET programmers, and my questions have nothing to do with VB.NET)

Protected Overrides Sub WndProc(ByRef msg As Message)
    Select Case msg.Msg
        Case 131 'WM\_NCCALCSIZE
            ...
        Case 132 'WM\_NCHITTEST
            ...
        Case 133 'WM\_NCPAINT
            Dim dc As Integer
            dc = GetDCEx(msg.HWnd.ToInt32(), msg.WParam.ToInt32(), 65536 + 128 + 1)
            Dim hdc As IntPtr = New IntPtr(dc)
            Dim g As Graphics = Graphics.FromHdc(hdc)
            OnPaintNonClient(New PaintEventArgs(g, Rectangle.Round(g.ClipBounds)))
            ReleaseDC(msg.HWnd.ToInt32(), hdc.ToInt32())
        Case 160 'WM\_NCMOUSEMOVE
            Dim pt As PointL
            pt.x = msg.LParam.ToInt32() Mod 65536
            pt.y = msg.LParam.ToInt32() / 65536
            Dim ppt As IntPtr = Marshal.AllocHGlobal(8)
            Marshal.StructureToPtr(pt, ppt, False)
            ScreenToClient(msg.HWnd.ToInt32(), ppt.ToInt32())
            pt = Marshal.PtrToStructure(ppt, GetType(PointL))
            Dim args As MouseEventArgs = New MouseEventArgs(MouseButtons.None, 0, pt.x, pt.y, 0)
            OnNonClientMouseMove(args)
            Marshal.FreeHGlobal(ppt)
        Case 161 'WM\_NCLBUTTONDOWN
            ...
        Case 162 'WM\_NCLBUTTONUP
            ...
        Case Else
            MyBase.WndProc(msg)
    End Select
End Sub

Protected Overridable Sub OnNonClientMouseMove(ByVal args As MouseEventArgs)
    If ... Then 'Test hotspots
        ...
        PostMessage(Me.Handle, 133, 0, 0) 'WM\_NCPAINT
    End If
End Sub

Protected Overridable Sub OnPaintNonClient(ByVal args As PaintEventArgs)
    ...
End Sub

[Kastro]

I tried something else out that gave me strange results as well... Instead of using PostMessage, I switched to using SendMessage. The WM_NCPAINT message is now reaching WndProc, however, the strange thing is that the drawing that I do there does not show up. The drawing code works fine in response to WM_NCPAINT messages caused by resizes, min/maxes, etc... Any ideas?