List
of Preprocessor Directives Available in C# (C Sharp)
If you want
compiler to perform certain actions at the time of compilation, you can
use preprocessors. In general, preprocessors are distinct from compilers.
Hence languages like C, C++ use preprocessors to define macros. But in
C#, preprocessors are merged with compilers and they are treated as a
single unit. C# has very limited set of preprocessors and they do not
support macros. This article will list the preprocessor directives supported
by C#.
Guidelines
to be Followed While Defining Preprocessor Directive:
• Syntax
for defining directives is:
# <directive name>
• # can be preceded and followed by blank spaces.
• Statement containing preprocessor directive should not end with
semicolon. No delimiter is required to end the statement.
• Single line comments (//) can follow the directive. But multi-line
comments (/* */) should not be used.
• No other C# code is allowed along with preprocessor directive in
the same line.
List of
C# Preprocessor Directives:
There are
altogether 12 preprocessor directives in C#. They are mentioned below:
• #define:
This directive will set its associated identifier to Boolean value “true”.
Its syntax is #define <identifier name>.
• #undef: This directive does the reverse process of #define directive.
#undef will reset its associated identifier to Boolean value “false”.
Its syntax is #undef <identifier name>.
• #if: This directive executes its associated block of code if and
only if the condition specified along with this directive is evaluated
to true. Its syntax is as follows:
#if <condition>
//Specific block of code
#endif
• #elif: Else-if conditions can be specified using #elif directive.
Block of code associated with #elif directive will be triggered if the
condition specified in this directive is evaluated to true and the condition
specified by its related if statement is evaluated to false. #elif block
is optional. Here’s the syntax of #elif directive:
#if <condition>
//Specific block of code
#elif <condition>
//else-if block of code
#endif
• #else: If conditions specified in #if and all its associated #elif
directives are not satisfied then the corresponding #else block will be
executed. #else block is optional. Syntax for #else directive is as follows:
#if <condition>
//Specific block of code
#else
//if condition fails, then control will come to this block of code
#endif
• #endif: If there is any #if directive, then corresponding #endif
directive is mandatory. Its syntax is already shown above along with #if,
#elif and #else directives.
• #error: This directive is used to throw an error. Its syntax is
#error <error message>.
• #warning: Instead of throwing an error and halting the program,
#warning directive is used to show warning message in the console and
it continues with the execution. Its syntax is #warning <warning message>.
• #pragma:
This directive controls the display of warning message specified using
#warning directive. Its syntax is #pragma disable/restore <warning
number>
• #line: Line number of corresponding source code displayed during
error and warning occurrence can be altered using this #line directive.
Its syntax is # line default or #line <modified line number> “<filename>”
• #region: You can specify a block of code as a region using this
directive. This region can then be accessed using visual code editors.
Its syntax is:
#region
<block of code>
#endregion
• #endregion: Each #region directive needs to be mapped to #endregion
directive. Its syntax is mentioned along with #region directive above.
