wpf截取屏幕

private void button1_Click(object sender, RoutedEventArgs e)
        {
            //调用
            IntPtr hDesk = GetDesktopWindow();
            IntPtr hSrce = GetWindowDC(hDesk);
            IntPtr hDest = CreateCompatibleDC(hSrce);
            IntPtr hBmp = CreateCompatibleBitmap(hSrce, (int)SystemParameters.PrimaryScreenWidth, (int)SystemParameters.PrimaryScreenHeight);
            IntPtr hOldBmp = SelectObject(hDest, hBmp);
            bool b = BitBlt(hDest, 0, 0, (int)SystemParameters.PrimaryScreenWidth, (int)SystemParameters.PrimaryScreenHeight, hSrce, 0, 0, CopyPixelOperation.SourceCopy | CopyPixelOperation.CaptureBlt);
            Bitmap bmp = Bitmap.FromHbitmap(hBmp);
            SelectObject(hDest, hOldBmp);
            DeleteObject(hBmp);
            DeleteDC(hDest);
            ReleaseDC(hDesk, hSrce);
            bmp.Save(@"c:\test.png");
            bmp.Dispose();
        }




        [DllImport("gdi32.dll")]
        static extern bool BitBlt(IntPtr hdcDest, int xDest, int yDest, int
        wDest, int hDest, IntPtr hdcSource, int xSrc, int ySrc, CopyPixelOperation rop);

        [DllImport("user32.dll")]
        static extern bool ReleaseDC(IntPtr hWnd, IntPtr hDc);
        [DllImport("gdi32.dll")]
        static extern IntPtr DeleteDC(IntPtr hDc);
        [DllImport("gdi32.dll")]
        static extern IntPtr DeleteObject(IntPtr hDc);
        [DllImport("gdi32.dll")]
        static extern IntPtr CreateCompatibleBitmap(IntPtr hdc, int nWidth, int nHeight);
        [DllImport("gdi32.dll")]
        static extern IntPtr CreateCompatibleDC(IntPtr hdc);
        [DllImport("gdi32.dll")]
        static extern IntPtr SelectObject(IntPtr hdc, IntPtr bmp);
        [DllImport("user32.dll")]
        public static extern IntPtr GetDesktopWindow();
        [DllImport("user32.dll")]
        public static extern IntPtr GetWindowDC(IntPtr ptr);