There are several different ways to get a screenshot. Generally speaking, for a text adapter, you can simply record the text from the screen as that will effectively be a screenshot (albeit one in text). If you need the colors and what not or want a true image, you will need to use some C#.
If you want just the text, I believe there is a ScreenText property (it has been a while) that will output all of the screen characters. You'll need to format this as it doesn't add line breaks, so if your screen is the standard 24x80, you'd simply break every 80 characters and insert a new line.
Here is an example solution that takes a screenshot of the main window of a given process. If you have multiple instances of a process, or want a screenshot of something other than the main window, you'll need some additional logic.