Windows Phone 8 应用内截图

            WriteableBitmap wb = new WriteableBitmap(this.LayoutRoot, new MatrixTransform());
            //wb.Render(this.LayoutRoot, new MatrixTransform());
            wb.Invalidate();
            using (System.IO.MemoryStream memoryStream = new System.IO.MemoryStream())
            {
                //Extensions.LoadJpeg();
                //Extensions.SaveJpeg(wb, memoryStream, wb.PixelWidth, wb.PixelHeight, 0, 100);
                //wb.LoadJpeg(System.IO.Stream);
                wb.SaveJpeg(memoryStream, wb.PixelWidth, wb.PixelHeight, , );
                memoryStream.Seek(, System.IO.SeekOrigin.Begin);
                new Microsoft.Xna.Framework.Media.MediaLibrary().SavePicture("hello.jpg", memoryStream);
            }

全屏幕截图快捷键是 开机键+home键