programming is more than syntax
There is a huge amount to programming .net that has nothing to do with the {}'s of C# and all to do with the .net framework (which won't translate to Ruby at all).
That said, a good/sharp programmer is more than a monkey slinging code so they should be able to work well in any language.
I think the mentality that programming has more to do with knowing your framework's features than it does with --- you know, how to program and stuff? That's part of what pisses people off about Rails devs.
The reality is, learning framework features is no different than learning how to mail-merge with your word processor. Sure, it's important. But it has nothing to do with whether someone's going to do a good job coding for you, 2 months in.
We looked for Ruby devs, quickly gave up, and wound up hiring a Lisp hacker. Our runner-up was a sharp C# hacker.