Looking around SO user profiles and other sites, I have noticed that some high profile users who work for Google including Jon Skeet use C# as their main programming language. Or at least, it is with C# / .Net related topics that they are most active.
This has led me to conclude, or at least assume, that C# is widely used inside Google.
I was under the impression that Google uses C++, PHP, and some other secret G-Programming language only available to Google insiders.
All in all, I could not have imagined they use any Microsoft-related tools or technologies.
My question is: which Google products are made using C#?
I believe your assumption is incorrect.
C# is not widely used at Google. In fact, from what I’ve heard, there is actually very minimal use of C# in any official Google project.