Preprocessing commands in C #

In C #, Preprocessor directives is a command that will not be executed and only affects the compilation process.
1. # region and # endregion define a set of statements for overall execution.
2. # define and # UNDEF definition symbols and delete definition symbols
3. # If, # endif, # else and # Elif conditional preprocessing commands (conditional Preprocessor directives)
4. # error and # warning are used to trigger errors and warnings. When an error occurs, the compiler stops the execution. Code . When a warning is issued, the compilation will continue.

1 # Define Symbol1
2 Using System;
3 Public   Class Class1
4 {
5 Public   Static   Void Main ()
6 {
7 # If Symbol1
8 Console. writeline ( " Symbol1 is defined " );
9 # Else
10 # Warning Symbol1 is not defined
11 # Endif
12 }
13 }