Hi Gayle, Does it matter what language you use in an interview with Google/Facebook/Amazon? Most of my recent experience has been with C# and thats the language I'm most comfortable with. I do have prior experience with C and C++ although in an interview would prefer to use C#. I'm not sure if that would be seen as a negative.
Like most things in interviews, it depends on your interviewer. Theoretically, as long as your resume lists C / C++, your interviewer could ask you to code in those. And they might, if they happen to have a favorite question that involved C or C++.
However, in general, that doesn't happen. Most candidates code in Java, and most interviewers are fine with that. C# is pretty close to Java - so close that your interviewers may not notice or care about your coding C#.
Still, I'd recommend that you brush up a bit on the few syntactical differences between C# and Java, so that you can code in Java for your interviews. Just explain to your interviewers the situation - most wouldn't care.