Extension methods are a godsent in C#. Really allow you to write extremely expressive code.
I cannot agree enough. This is not new for any C# dev.
Expressiveness is not as great as ruby, but certainly on par with Rust
LINQ extension methods by Jon Skeet - https://code.google.com/p/morelinq/
I would recommend reading this stackoverflow post to see some great extension methods.
http://stackoverflow.com/questions/271398/what-are-your-favo...