#region 獲取windows桌面背景
        [System.Runtime.InteropServices.DllImport("user32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto, SetLastError = true)]
        public static extern int SystemParametersInfo(int uAction, int uParam, StringBuilder lpvParam, int fuWinIni);

        private const int SPI_GETDESKWALLPAPER = 0x0073;
        #endregion

void WindowsBtn_Click(object sender, RoutedEventArgs e)
        {
            //定義存儲緩沖區大小
            StringBuilder s = new StringBuilder(300);
            //獲取Window 桌面背景圖片地址，使用緩沖區
            SystemParametersInfo(SPI_GETDESKWALLPAPER, 300, s, 0);
            //緩沖區中字符進行轉換
            string wallpaper_path = s.ToString(); //系統桌面背景圖片路徑
         }