This section discusses the C# language's preprocessor directives:

#if

#else

#elif

#endif

#define

#undef

#warning

#error

#line

#region

#endregion

#pragma

#pragma warning

#pragma checksum

While the compiler does not have a separate preprocessor, the directives described in this section are processed as if there was one; these directives are used to aid in conditional compilation. Unlike C and C++ directives, you cannot use these directives to create macros.

A preprocessor directive must be the only instruction on a line.