//全屏程式碼：
private void Window_Loaded(object sender, RoutedEventArgs e)

{
    // 設定全屏
    this.WindowState = System.Windows.WindowState.Normal;
    this.WindowStyle = System.Windows.WindowStyle.None;
    this.ResizeMode = System.Windows.ResizeMode.NoResize;
    this.Topmost = true;

    this.Left = 0.0;
    this.Top = 0.0;
    this.Width = System.Windows.SystemParameters.PrimaryScreenWidth;
    this.Height = System.Windows.SystemParameters.PrimaryScreenHeight;
}
 

 擴充套件類：

專案先引用下面dll：

1：System.Windows.Forms; 2：System.Drawing;

public static class ExpendMethod
    {
        private static Window _fullWindow;
        private static WindowState _windowState;
        private static WindowStyle _windowStyle;
        private static bool _windowTopMost;
        private static ResizeMode _windowResizeMode;
        private static Rect _windowRect;

        /// <summary>
        /// 進入全屏    
        /// </summary>
        /// <param name="window"></param>
        public static void GoFullscreen(this Window window)
        {
            //已經是全屏 
            if (window.IsFullscreen()) return;

            //儲存窗體資訊       
            _windowState = window.WindowState;
            _windowStyle = window.WindowStyle;
            _windowTopMost = window.Topmost;
            _windowResizeMode = window.ResizeMode;
            _windowRect.X = window.Left;
            _windowRect.Y = window.Top;
            _windowRect.Width = window.Width;
            _windowRect.Height = window.Height;


            //變成無邊窗體 
            window.WindowState = WindowState.Normal;//假如已經是Maximized，就不能進入全屏，所以這裡先調整狀態 
            window.WindowStyle = WindowStyle.None;
            window.ResizeMode = ResizeMode.NoResize;
            window.Topmost = true;//最大化後總是在最上面 

            //獲取視窗控制代碼 
            var handle = new WindowInteropHelper(window).Handle;
            //獲取當前顯示器螢幕
            Screen screen = Screen.FromHandle(handle);

            //調整視窗最大化,全屏的關鍵程式碼就是下面3句 
            window.MaxWidth = screen.Bounds.Width;
            window.MaxHeight = screen.Bounds.Height;
            window.WindowState = WindowState.Maximized;

            //解決切換應用程式的問題
            window.Activated += new EventHandler(window_Activated);
            window.Deactivated += new EventHandler(window_Deactivated);
            //記住成功最大化的窗體 
            _fullWindow = window;
        }

        static void window_Deactivated(object sender, EventArgs e)
        {
            var window = sender as Window;
            window.Topmost = false;
        }
        static void window_Activated(object sender, EventArgs e)
        {
            var window = sender as Window;
            window.Topmost = true;
        }

        /// <summary>
        /// 退出全屏
        /// </summary>
        /// <param name="window"></param>
        public static void ExitFullscreen(this Window window)
        {
            //已經不是全屏無操作 
            if (!window.IsFullscreen()) return;
            //恢復視窗先前資訊，這樣就退出了全屏 
            window.Topmost = _windowTopMost;
            window.WindowStyle = _windowStyle;
            window.ResizeMode = ResizeMode.CanResize;//設定為可調整窗體大小 
            window.Left = _windowRect.Left;
            window.Width = _windowRect.Width;
            window.Top = _windowRect.Top;
            window.Height = _windowRect.Height;
            window.WindowState = _windowState;//恢復視窗狀態資訊 
            window.ResizeMode = _windowResizeMode;//恢復視窗可調整資訊 
            //移除不需要的事件 
            window.Activated -= window_Activated;
            window.Deactivated -= window_Deactivated;
            _fullWindow = null;
        }

        /// <summary>
        /// 窗體是否在全屏狀態
        /// </summary>
        /// <param name="window"></param>
        /// <returns></returns>
        public static bool IsFullscreen(this Window window)
        {
            if (window == null)
                throw new ArgumentNullException("window");
            return _fullWindow == window;
        }
    }