public static extern void DwmExtendFrameIntoClientArea(IntPtr hWnd, ref Margin pMargins);
private void ExtendFrameIntoClient() { _margin = new Margin { cxLeftWidth = X, cxRightWidth = Width, cyBottomHeight = Height, cyTopHeight = Y }; NativeMethods.DwmExtendFrameIntoClientArea(Handle, ref _margin); }