Earlier quoted context omitted.
I think you have the option of taking the test in Java, C++ or Python. I hadn't heard of the C# option. Thank you for mentioning the same.
At my in-person interview at Google, they told me I could use whatever I felt most comfortable with, which at that point in time was Objective-C. In retrospect it was a terrible idea. That language is stupid verbose, and I ran out of whiteboard for every single question I had there. They were mainly interested in me for iOS development though. They did not give me an offer, although I don't think it was for that reas…
Personally, I think that C# is the ideal language for interviewing in, as the .NET standard library is very powerful. SortedDictionary alone can easily polish off entire classes of interview questions, and the same can be said for pretty simply LINQ statements. I actually solved one problem so trivially using a combination of the right data structure and LINQ that the interviewer asked me to provide an alternate imperative implementation of the LINQ statement, just so he could see that I actually knew how to implement something like that rather than just use it.
You can approach similar levels of power with use of Java 8's Streams APIs and a good collections library like Guava, but Guava is only likely to be understood by a majority of interviewers at Google, whereas the C# standard library should be understood by a majority of C# interviewers everywhere.
It's absolutely worth spending a few hours brushing up on a "better" interviewing language and then using that rather than using a less optimal language just because it happens to be all you've used recently.