Converting VB.NET Preprocessor Directives to C# Preprocessor Directives

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5.00/5 (1 vote)

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I am porting some VB.NET code to C#.
Here is the VB.NET

VB

#If _MyType = "WindowsForms" Then
     'Some things to do ...
#End If

From what I have read C# will only deal with boolean #IF statements
Apparently it is because the compiler does not like this:

C#

#if _MyType = "WindowsForms"
      //Some things to do ...
#endif

How can I achieve the same results?

Posted 14-Feb-11 11:07am

MacIntyre

Updated 14-Feb-11 12:10pm

Manfred Rudolf Bihy

v3

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Manfred Rudolf Bihy 14-Feb-11 18:10pm

Edit: Added pre tags.

2 solutions

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Nish Nishant · Accepted Answer · 2011-02-14T11:13:00

The C# equivalent would be to define WindowsForms and then to do this:

C#

#if WindowsForms

      // do stuff here

#endif

You can define a symbol either via #define or via the project settings.

Example of doing it in code:

C#

#define WindowsForms

[Edit]
~~~~~~~~~~

The #define has to come before any other tokens in the source file. Example:

C#

#define WindowsForms

using System;

namespace Nothing
{
    class Program
    {
        static void Main(string[] args)
        {
#if WindowsForms
            Console.WriteLine("WindowsForms defined");
#else
            Console.WriteLine("WindowsForms not defined");
#endif
        }
    }

}

Basically the #if check checks to see if the symbol is defined. It cannot check for a value. It only checks for definition.

Manfred Rudolf Bihy · Accepted Answer · 2011-02-14T11:20:00

Solution 2

The details about preprocessor directives are here: http://msdn.microsoft.com/en-us/library/ed8yd1ha(v=VS.80).aspx[^]
If you read carefully on the site I posted you'll find that this page gives you an interview of all available operators: http://msdn.microsoft.com/en-us/library/4y6tbswk(v=vs.71).aspx[^]

That should fix your problems. ("==" for equality not just "=")

Cheers!

Posted 14-Feb-11 11:20am

Manfred Rudolf Bihy

Comments

Sergey Alexandrovich Kryukov 14-Feb-11 17:21pm

My 5,
--SA

Nish Nishant 14-Feb-11 17:23pm

While == is allowed I cannot see how it can be used. VB has a #const which C# does not have.

Manfred Rudolf Bihy 14-Feb-11 17:44pm

So true! The MSDN page for 2005 had no hint but as I looked at the documentation of 2008 and 2010 they said in C# == can only be used for boolean compares. My bad! :(

Nish Nishant 14-Feb-11 17:48pm

Yeah, and even the bool comparison doesn't really provide any useful feature in C# as far as I can see.

I guess this is one area where VB.NET has a slight edge over C#.

MacIntyre 14-Feb-11 17:38pm

Ok - so far so good
The only problem is when I: #define WindowsForms = "WindowsForms";
the #define gets an error saying it can not be used after the first token
What does that mean and where does it go I tried several locations the would still be with in scope.
Thanks..

Nish Nishant 14-Feb-11 17:47pm

That's not how you do it. You do it as:

#define WindowsForms

MacIntyre 14-Feb-11 18:11pm

It still does not like the #define no matter where I place it in the source code?
When I say #define WindowsForm what is the content of WindowsForm so the a comparison to anything will yeild something workable?

Nish Nishant 14-Feb-11 18:15pm

Check my updated answer.

MacIntyre 14-Feb-11 18:23pm

I'm sorry if I seem thick headed today or unable to communicate the problem.
Now I have:
#define WindowsForm
#If (_MyType == WindowsForm)
....
#endif

The compiler if not complaining about the #If statement it is complaining about the #define WindowsForm statement

Nish Nishant 14-Feb-11 18:24pm

Yes, you can do that in VB.NET. You cannot do that in C#. VB.NET supports some functionality that is not supported by C#.

Nish Nishant 14-Feb-11 18:25pm

Ok, sorry - I misinterpreted your comment - the reason it complains about the #define is that it has to be at the top of your C# source file.

But you still have a problem in your #if too. You need to fix both. Please read my updated answer.

MacIntyre 14-Feb-11 18:37pm

Ok. I looked at you code and understand what is there. What I do not understand is by having the #define directive at the top of the source file the #If WindowsForm statement will never fail because the #define statement is there. The problem is how do I determine if this dll is being called by a WinApp or WebApp or ConsoleApp..

Nish Nishant 14-Feb-11 18:58pm

In C#, as far as I know, there are no predefined preprocessor symbols for determining the subsystem.

MacIntyre 14-Feb-11 18:29pm

I have solved the problem...
the #define directive most be placed outside the namespace.
Thanks for everyone assistance..

Manfred Rudolf Bihy 14-Feb-11 17:47pm

Please regard Nishants answer. I proposed it as the solution to your problem.

Espen Harlinn 14-Feb-11 18:04pm

Good answer :)