You can copy the snippet. Explanation: The Bitmap is a constructor node, and you give it the image reference. Then you get the data, in this case, one RGB pixel at 0,0. If this works, the bitmap object has a method that returns the handle to the data.
Edit: The Bitmap constructor is in System.drawing.
If you are worried about tearing (capturing data from 2 different frames) you can use the PictureBox' VisibleChanged LoadCompleted callback.