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#Define Compiler Directive in C#

In C, I could declare a compiler directive as follows:

#define MY_NUMBER 10

However, in C#, I only appear to be able to do this:

#define MY_NUMBER

Which is obviously useless in this case.

Is this correct, or am I doing something wrong? If not, can anyone suggest a way of doing this, either at namespace or solution level? I thought of maybe creating a static class, but that seems to be overkill for one value.

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Paul Michaels Avatar asked Jun 10 '10 08:06

Paul Michaels


4 Answers

Yes, it is correct.

Here's a quote from the MSDN documentation:

The pre-processing directives provide the ability to conditionally skip sections of source files, to report error and warning conditions, and to delineate distinct regions of source code. The term "pre-processing directives" is used only for consistency with the C and C++ programming languages. In C#, there is no separate pre-processing step; pre-processing directives are processed as part of the lexical analysis phase.

So you can't really define compiler constants, like in C and C++.

Related resources:

  • Pre-processing directives
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Enrico Campidoglio Avatar answered Nov 02 '22 08:11

Enrico Campidoglio


A lot of the other answers suggest using a public const field. Note however that a public const will be compiled into assemblies referencing it, forcing you to recompile not only the assembly it is defined in but also every assembly referencing it if you ever change the value of the const.

If you are not certain the value will never have to change, a public static readonly field is a better alternative.

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josef.axa Avatar answered Nov 02 '22 09:11

josef.axa


Yes, you're correct. const and readonly are really your only options.

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Matthew Flaschen Avatar answered Nov 02 '22 07:11

Matthew Flaschen


You can define a const or a static readonly, and if you want it conditionally you can wrap it in an #if directive

#if DEBUG
private const int MY_NUMBER = 10;
#else
private const int MY_NUMBER = 20;
#endif
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Thomas Avatar answered Nov 02 '22 07:11

Thomas