private static extern bool _GetWindowRect(IntPtr hWnd, out RECT lpRect);

        public static RECT AdjustWindowRectEx(RECT lpRect, WS dwStyle, bool bMenu, WS_EX dwExStyle)
        {
            // Native version modifies the parameter in place.
            if (!_AdjustWindowRectEx(ref lpRect, dwStyle, bMenu, dwExStyle))
            {
                HRESULT.ThrowLastError();
            }

            return lpRect;
        }

 public static IntPtr CreateRectRgnIndirect(RECT lprc)
 {
     IntPtr ret = _CreateRectRgnIndirect(ref lprc);
     if (IntPtr.Zero == ret)
     {
         throw new Win32Exception();
     }
     return ret;
 }

 private static extern bool _AdjustWindowRectEx(ref RECT lpRect, WS dwStyle, [MarshalAs(UnmanagedType.Bool)] bool bMenu, WS_EX dwExStyle);

 public static RECT Union(RECT rect1, RECT rect2)
 {
     return new RECT
     {
         Left = Math.Min(rect1.Left, rect2.Left),
         Top = Math.Min(rect1.Top, rect2.Top),
         Right = Math.Max(rect1.Right, rect2.Right),
         Bottom = Math.Max(rect1.Bottom, rect2.Bottom),
     };
 }

        private RECT _GetAdjustedWindowRect(RECT rcWindow)
        {
            // This should only be used to work around issues in the Framework that were fixed in 4.0
            Assert.IsTrue(Utility.IsPresentationFrameworkVersionLessThan4);

            var style = (WS)NativeMethods.GetWindowLongPtr(_hwnd, GWL.STYLE);
            var exstyle = (WS_EX)NativeMethods.GetWindowLongPtr(_hwnd, GWL.EXSTYLE);

            return NativeMethods.AdjustWindowRectEx(rcWindow, style, false, exstyle);
        }

        private static RECT AdjustWorkingAreaForAutoHide(IntPtr monitorContainingApplication, RECT area)
        {
            // maybe we can use ReBarWindow32 isntead Shell_TrayWnd
            IntPtr hwnd = NativeMethods.FindWindow("Shell_TrayWnd", null);
            IntPtr monitorWithTaskbarOnIt = NativeMethods.MonitorFromWindow(hwnd, (uint)MonitorOptions.MONITOR_DEFAULTTONEAREST);

            var abd = new APPBARDATA();
            abd.cbSize = Marshal.SizeOf(abd);
            abd.hWnd = hwnd;
            NativeMethods.SHAppBarMessage((int)ABMsg.ABM_GETTASKBARPOS, ref abd);
            bool autoHide = Convert.ToBoolean(NativeMethods.SHAppBarMessage((int)ABMsg.ABM_GETSTATE, ref abd));

            if (!autoHide || !Equals(monitorContainingApplication, monitorWithTaskbarOnIt))
            {
                return area;
            }

            switch (abd.uEdge)
            {
                case (int)ABEdge.ABE_LEFT:
                    area.Left += 2;
                    break;
                case (int)ABEdge.ABE_RIGHT:
                    area.Right -= 2;
                    break;
                case (int)ABEdge.ABE_TOP:
                    area.Top += 2;
                    break;
                case (int)ABEdge.ABE_BOTTOM:
                    area.Bottom -= 2;
                    break;
                default:
                    return area;
            }
            return area;
        }

 public static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);