Hmm, I've been following the tutorial to the second page now, and I had some problems. Luckily for me, I was smart enough to solve them. These problems were not mine, they were derik's...(but I won't critisize since I'm clueless on how to do anything in
C# unless it's in a detailed step by step tutorial).
Anyways, you need to add this to the using commands-
And somewhere after the render loop you should have this empty thing-