C#

private const int	DCX_WINDOW=0x0001;
private const int	DCX_INTERSECTRGN=0x0080;

[System.Runtime.InteropServices.DllImport("user32.dll")]
private static extern IntPtr GetDCEx(IntPtr hWnd, IntPtr hrgnClip, int flags);

protected override void WndProc(ref Message m)
{
	switch (m.Msg)
	{
		case WM_NCPAINT:
		{
			Debug.WriteLine("WM_NCPAINT");

			Graphics		gr=Graphics.FromHdc(GetDCEx(m.HWnd, m.WParam, DCX_WINDOW|DCX_INTERSECTRGN));

			ControlPaint.DrawButton(gr, 60, 1, 5, 5, ButtonState.Normal);

			break;
		}
	}
	
	base.WndProc(ref m);
}

Graphics		gr=Graphics.FromHdc(GetDCEx(m.HWnd, m.WParam, DCX_WINDOW|DCX_INTERSECTRGN));

IntPtr hdc = GetDCEx(m.HWnd, m.WParam, DCX_WINDOW|DCX_INTERSECTRGN);
Graphics g = Graphics.FromHdc(hdc);

[ComImport, Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"),
  InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IHTMLElementRender
{
  void DrawToDc(IntPtr hdc);
  void SetDocumentPrinter(
    [MarshalAs(UnmanagedType.BStr)] string printerName, IntPtr hdc);
}

IntPtr ptr = Marshal.GetComInterfaceForObject(element,
  typeof(IHTMLElementRender)); // Interface type from above
IHTMLElementRender render = (IHTMLElementRender)Marshal.GetObjectForIUnknown(
  ptr);
render.DrawToDc(hdc);
// IUknown::Release will be called when 'render' is GC'd, but you must
// release the IntPtr from GetComInterfaceForObject.
Marshal.Release(ptr);

"If a man empties his purse into his head, no man can take it away from him, for an investment in knowledge pays the best interest." -- Joseph E. O'Donnell

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Can't manage to P/Invoke that Win32 API in .NET? Why not do interop the wiki way!