title: How do screenshot in c# (low level may be) when desktop blocked?
body: <p>I try get screenshot (windows 8) with code and get black screen when desktop blocked:</p>
  
  <pre><code>    public static Bitmap ImageFromScreen()
      {
          Graphics gr;
          Bitmap bmp = new Bitmap(Screen.PrimaryScreen.Bounds.Width, 
              Screen.PrimaryScreen.Bounds.Height,PixelFormat.Format32bppRgb);
          gr = Graphics.FromImage(bmp);
          gr.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y,
              0, 0, Screen.PrimaryScreen.Bounds.Size, CopyPixelOperation.SourceCopy);
          return bmp;
      }
  </code></pre>