C# #if Preprocessing Directive
In this chapter you will learn:
- How to use Preprocessing Directives #if
- Syntax for #if Preprocessing Directive
- Example for #if Preprocessing Directive
- Use #if with #else
Description
The #if and #endif directives
enable conditional compilation.
A symbol is true if it has been defined.
A symbol is false if it has not been defined.
If a symbol has been defined by a #define directive, the symbol true.
Syntax
The general form of #if is
#if symbol-expression
statement sequence
#endif
Example 1
#define AAA//from www . j av a 2 s. c om
using System;
class MainClass {
public static void Main() {
#if AAA
Console.WriteLine("Compiled for experimental version.");
#endif
Console.WriteLine("This is in all versions.");
}
}
The code above generates the following result.
Example 2
Use #if with #else
#define AAA //from www. j av a 2 s . c o m
#define BBB
using System;
class Test {
public static void Main() {
#if AAA
Console.WriteLine("Compiled for AAA version.");
#else
Console.WriteLine("Compiled for release.");
#endif
#if AAA && BBB
Console.Error.WriteLine("Testing AAA and BBB version.");
#else
Console.Error.WriteLine("Not (AAA and BBB) version.");
#endif
Console.WriteLine("This is in all versions.");
}
}
The code above generates the following result.
Next chapter...
What you will learn in the next chapter:
- How to use Preprocessing Directive #elif
- Syntax for #elif Preprocessing Directive
- Example for #elif Preprocessing Directive