#480 – Pre-Processing Directives

Pre-processing directives are elements that you can include in your source code that are not part of the source code itself.  Instead, they instruct the C# compiler to perform some particular action, like skipping compilation of a section of the code.

The pre-processing directives available in C# include:

• #define/#undef – Define/undefine condition compilation symbols (see #if)
• #if/#elif/#else/#endif – Skip compilation of a section of code based on the existence of a conditional compilation symbol
• #line – specifies a line number to use when reporting errors
• #error – issue errors during compilation
• #warning – issue warnings during compilation
• #region/#endregion – define a collapsible code region, to improve readability
• #pragma warning – disable or restore certain compiler warnings
• #pragma checksum – generate a checksum for an ASP.NET page, for debugging purposes