Where can I find good beginner stuff on it, and perhaps an online sandbox?
I have not written anything in C# before.
I have experience in Pascal & Java, but not much. I have written a few handful webpages with some JS using very little jQuery and mostly ESRI's JS API which is based off Dojo. I did some stuff in C and C++ but that's pretty much redundant now since I haven't written anything in it in a long time.