Learning a new language isn't always fun, especially Javascript.  Plus, when you're working in one language, it takes context switching to flip to another, even for a trivial task.  Nikhil Kothari, an architect on the Web Platform and Tools team at Microsoft, has created something called Script#, which allows you to program in C# while compiling to Javascript/Ajax.

ZDnet has a good blog post on the importance of this technology, and a brief comparison with the Google version which compiles Java to Javascript.