Having trouble converting this line of vb code into C#

Question

I have a vb.net project I'm trying to convert into C#. I have a file named MyWebExtension.vb and in it there is this line of code #If _MyType <> "Empty" Then

I attempted to convert into C# #if (_MyType != "Empty")

When I run the application I get the following error:

Invalid preprocessor expression.

What did I do wrong with my conversion?

Answer 1

#define in C# can only specify 'flags', not constant values as VB allows you to do.

In C#, you can have:

#define _MyType

#If _MyType

or:

#if ! _MyType

but in VB, you can have:

#Const _MyType = "SomeType"

#If _MyType = "SomeType"

There is no good work-around for this - you can use constants, but of course these can only be referenced from within a class.

Answer 2

From Compiler Error CS1517

The following sample shows some valid and invalid preprocessor expressions:

#if symbol      // OK
#endif
#if !symbol     // OK
#endif
#if (symbol)    // OK
#endif
#if true        // OK
#endif
#if false       // OK
#endif
#if 1           // CS1517
#endif
#if ~symbol     // CS1517
#endif
#if *           // CS1517
#endif

class x
{
   public static void Main()
   {
   }
}

So I think you can use like this;

#define _MyType

#If _MyType

From #if

When the C# compiler encounters an #if directive, followed eventually by an #endif directive, it will compile the code between the directives only if the specified symbol is defined . Unlike C and C++, you cannot assign a numeric value to a symbol; the #if statement in C# is Boolean and only tests whether the symbol has been defined or not.

#define DEBUG
// ...
#if DEBUG
    Console.WriteLine("Debug version");
#endif

You can use the operators == (equality), != (inequality) only to test for true or false . True means the symbol is defined . The statement -#if DEBUG has the same meaning as #if (DEBUG == true). The operators && (and), and || > (or) can be used to evaluate whether multiple symbols have been defined. You can also group symbols and operators with parentheses.