Identifiers are names programmers choose for their types, methods, variables, and so on. An identifier must be a whole word, essentially composed of Unicode characters starting with a letter or underscore. An identifier must not clash with a keyword. As a special case, the @ prefix can be used to avoid such a conflict, but the character isn’t considered part of the identifier that it precedes. For instance, the following two identifiers are equivalent:

C# identifiers are case-sensitive, but for compatibility with other languages, you should not differentiate public or protected identifiers by case alone.