Mastering C# — Preprocessor Directives

Preprocessor directives are commands in C# that are processed before the actual compilation of code begins. They instruct the compiler to perform specific pre-compilation tasks, such as conditional compilation, region organization, or including external resources. These directives begin with a # symbol and do not require a semicolon (;) at the end.

Photo by Bermix Studio on Unsplash

Common Preprocessor Directives in C#

1. #define and #undef

• #define creates a symbolic constant for conditional compilation. Unlike constants in C#, these are not visible at runtime.
• #undef removes a symbolic constant.

#define DEBUG
// Later in the code
#undef DEBUG

2. #if, #else, #elif, and #endif

• These are used for conditional compilation. The compiler will only compile the code between these directives if the specified condition is true.

#define DEBUG
#if DEBUG
    Console.WriteLine("Debug version");
#endif

3. #warning and #error

• #warning allows you to generate a custom compiler warning.
• #error generates a compiler error. Compilation stops if an #error directive is reached

#warning This is a warning message
#error This is an error…