/// <summary>
/// Saves a screen capture in the specified image format to a file.
/// </summary>
/// <param name="filename"></param>
/// <param name="format"></param>
private void SaveScreenShot(string filename, ImageFormat format)
{
        Bitmap screenShot = CaptureScreenShot();
 
  	screenShot.Save(filename, format);
}
 
/// <summary>
/// Saves a picture of the screen to a bitmap image.
/// </summary>
/// <returns>The saved bitmap.</returns>
private Bitmap CaptureScreenShot()
{
 	// get the bounding area of the screen containing (0,0)
        // remember in a multidisplay environment you don't know which display holds this point
    	Rectangle bounds = Screen.GetBounds(Point.Empty);
 
    	// create the bitmap to copy the screen shot to
   	Bitmap bitmap = new Bitmap(bounds.Width, bounds.Height);
 
    	// now copy the screen image to the graphics device from the bitmap
   	using (Graphics gr = Graphics.FromImage(bitmap))
   	{
       	   gr.CopyFromScreen(Point.Empty, Point.Empty, bounds.Size);
   	}
 
  	return bitmap;
}

//save screen shot in PNG image format
SaveScreenShot("MyScreenShot.png", ImageFormat.Png);

/// <summary>
/// Saves a screen capture of the specified control to a file.
/// </summary>
/// <param name="control"></param>
/// <param name="filename"></param>
/// <param name="format"></param>
private void SaveControlShot(Control control, string filename, ImageFormat format)
{
   	Bitmap controlShot = CaptureControlShot(control);
 
   	controlShot.Save(filename, format);
}
 
/// <summary>
/// Gets a bitmap image of the specified control.
/// </summary>
/// <param name="control"></param>
/// <returns></returns>
private Bitmap CaptureControlShot(Control control)
{
        // get control bounding rectangle
     	Rectangle bounds = control.Bounds;
 
   	// create the new bitmap that holds the image of the control
     	Bitmap bitmap = new Bitmap(bounds.Width, bounds.Height);
 
   	// copy controls image data to the bitmaps graphics device
    	using (Graphics gr = Graphics.FromImage(bitmap))
    	{
        	gr.CopyFromScreen(control.Location, Point.Empty, bounds.Size);
     	}
 
    	return bitmap;
}

// if "this" is a control, like a form
SaveControlShot(this, "MyControlShot.png", ImageFormat.Png);