How to make screenshot in C#

 
  [DllImport("user32.dll", SetLastError = true)]
  static extern IntPtr GetDC(IntPtr hWnd);
  [DllImport("user32.dll", SetLastError = true)]
  static extern IntPtr WindowFromDC(IntPtr hdc);
  [DllImport("user32.dll")]
  static extern bool GetWindowRect(IntPtr hWnd, ref RECT rect);
  [DllImport("gdi32.dll", EntryPoint = "BitBlt", SetLastError = true)]
  [return: MarshalAs(UnmanagedType.Bool)]
  static extern bool BitBlt([In] IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, [In] IntPtr hdcSrc, int nXSrc, int nYSrc, uint dwRop);

 var src = GetDC(IntPtr.Zero);
 RECT r = new RECT();
 GetWindowRect(WindowFromDC(src), ref r);
 int rW = 2*(r.Right — r.Left); // because we don’t want to get exact DPI scaling
 int rH = 2*(r.Bottom — r.Top);
 
 var bmp = new Bitmap(rW, rH);
 var g = System.Drawing.Graphics.FromImage(bmp);
 var dst = g.GetHdc();
 
 BitBlt(dst, 0, 0, rW, rH, src, 0, 0, 0x00CC0020);
 g.ReleaseHdc(); 
 bmp.Save(“screengrab.png”, System.Drawing.Imaging.ImageFormat.Png);