Question...D-2 to D-1???

As many on this board know, I have always been intrigued by a lot of the D-2 players I see in these games. Why is it that we never hear about a D-2 player moving up to the D-1 ranks? I have seen some really good D-2 players at some of these programs. Some I would like to see in a Flyer uniform. Are they allowed to make that jump?