private void MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            switch (e.ClickCount)
            {
                case 1://单击
                    {
                        NativeMethods.SendMessage(Hwnd, (int)WindowMessages.WM_NCLBUTTONDOWN, (IntPtr)HitTest.HTCAPTION, IntPtr.Zero);
                        break;
                    }
                case 2://双击
                    {
                        WindowState = WindowState == WindowState.Maximized ? WindowState.Normal : WindowState.Maximized;
                        break;
                    }
            }