Does the C# language localize for people that have their machine's set to some language other than English?
In other words, is C# always unconditionally written in English?
C# is standardized in the C# Language Specification (ECMA-334).
There's only one set of keywords (English) and is the same for everybody. The .NET Framework (which is not part of the C# language) also uses English for all class and method names.
Of course, you may name your variables and method names as you like. C# supports the whole range of Unicode characters.