//mw为主窗体

 public FullWindow(Window mw)

        {

            InitializeComponent();

            this.Width = System.Windows.SystemParameters.PrimaryScreenWidth;

            this.Height = System.Windows.SystemParameters.PrimaryScreenHeight;

            this.Left = 0;

            this.Top = 0;

            this.MouseDown+=

            delegate{

                this.Close();

                if (mw != null && mw.Visibility == Visibility.Hidden)

                    mw.Show();

            };

            double iHeight = System.Windows.SystemParameters.PrimaryScreenHeight;

            double iWidth = System.Windows.SystemParameters.PrimaryScreenWidth;

            //创建一个和屏幕一样大的bitmap

            System.Drawing.Image img = new Bitmap((int)iWidth, (int)iHeight);

            //从一个继承自image类的对象中创建Graphics对象

            Graphics g = Graphics.FromImage(img);

            //抓取全屏幕

            g.CopyFromScreen(new System.Drawing.Point(0, 0), new System.Drawing.Point(0, 0), new System.Drawing.Size((int)iWidth, (int)iHeight));

            tpath= AppDomain.CurrentDomain.BaseDirectory.Replace(@"bin\Debug", "Images") + "1.bmp";

            img.Save(tpath, ImageFormat.Bmp);

            //以下代码将img设置为全屏窗体的背景图片。