In C#, there is no direct equivalent to the C preprocessor directive #ifndef (which stands for “if not defined”). However, you can achieve similar functionality using conditional compilation symbols and the #if directive.
In C#, you can define conditional compilation symbols using the #define directive, and you can check if a symbol is defined using the #if directive. Here’s an example:
#define SYMBOL_NAME
#if SYMBOL_NAME
// Code to execute if SYMBOL_NAME is defined
#else
// Code to execute if SYMBOL_NAME is not defined
#endif
In this example, if the SYMBOL_NAME symbol is defined using #define SYMBOL_NAME, the code inside the #if block will be executed. Otherwise, the code inside the #else block will be executed.
Note that conditional compilation symbols are usually defined at the project level or using compiler flags, so you have more control over when and where they are defined.