There are various online converters that will do the job with varying degrees of success. A search should turn them up. None of them will 100% though.
SharpDevelop is a free .NET IDE that can convert code I believe, although I've never used it so I don't know how effective it is. I'd guess it would be better than the online offerings and it would work with more than snippets.
I use
Instant C# and you'll find that it is pretty close to 100% accurate, even for complex code involving new features. There is a free trial but it has limitations. If you will use it regularly then it's definitely worth the price.