C# Utility Class - Setting up for General Use and Compiling w/o Main

Question

Okay, so working on learning some C#. Great language, love working with it in general, but I'm not understanding how to get over this lack of utility classes. In essence, I want to set up a general utilities class that can be contained in a folder and used for any project simply by doing a "using namespace Globals/Utilities/etc." command. In essence:

using System;
namespace Globals {
    public static class Commands {
        public static void WaitForReturn() {
            Console.WriteLine("Press Enter to continue.");
            Console.ReadLine();
        }
    }
}

Similar to the above, such that in any other class I can call the functions by including it as a preprocessing directive.

using System;
using Globals;

namespace RectangleDemo {
    <rectangle definition here>

    class Demo {
        static void Main(string[] args) {
            Rectangle r = new Rectangle();
            Rectangle s = new Rectangle(5, 6);
            r.Display();
            s.Display();
            WaitForReturn();
        }
    }
}

As it is, I'm trying to simply compile my 'utility' class (with more than what is listed above) to check for errors, but it's just telling me that it can't compile it because there's no main method. Any suggestions?

(Yes I'm aware I have a java coding style, I'm okay with that!)

Create the project as a Class Library. By definition, class libraries are not exectuables and do not have a main (or other entry point), but are intended to be used by applications as a referenced assembly. — Tim, Jun 10 '16 at 23:11
@Tim I'm actually doing this through sublime text and command prompt compiling just to get my hands dirty with actually compiling the code. My Visual Studio actually has a problem with creating C# projects in that it crashes whenever I try to create one, but that's a problem I've been trying to take up with Microsoft haha — Jonathan McDevitt, Jun 11 '16 at 17:50

score 5 · Answer 1 · answered Jun 10 '16 at 23:11

With C#6 you can import static methods so you can end up with the following coding style:

using System;
using static Globals.Commands;

namespace MyConsole
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            WaitForReturn();
        }
    }
}

namespace Globals
{
    public static class Commands
    {
        public static void WaitForReturn()
        {
            Console.WriteLine("Press Enter to continue.");
            Console.ReadLine();
        }
    }
}

And as suggested by Tim, if you don't want a main entry point, use a Class Library project instead of a Console Application.

Along with Atif's answer, this is extremely informative, thank you very much =) — Jonathan McDevitt, Jun 11 '16 at 17:55

score 2 · Accepted Answer · answered Jun 10 '16 at 23:53

C# doesn't work the way you're expecting. There is no relationship between importing namespaces/classes and files so doing using Globals; does not translate to file content inclusion à la C/C++ (i.e. not the same as #include "Globals.cs").

On the command line, the C# compiler accepts the list of files that make up your sources:

csc Demo.cs Globals.cs

If you are using an IDE like Visual Studio, you would link the Globals.cs into your project. And by link, I mean more like a symbolic link (though it is not in actual fact) than static linking via a linker as you would have typically in a C/C++ setup.

So to make your scenario of “inclusion of common code” work, you need to compile by simply always adding Globals.cs to the list of C# files making up your project (supplied to the compiler on the command line or added to your project in IDE) and then using a static import:

using System;
using static Globals.Commands; // <-- import statically allows methods to be
                               //     used without class name qualification

namespace RectangleDemo {
    // <rectangle definition here>

    class Demo {
        static void Main(string[] args) {
            Rectangle r = new Rectangle();
            Rectangle s = new Rectangle(5, 6);
            r.Display();
            s.Display();
            WaitForReturn();
        }
    }
}

A very informative answer, thanks a lot! Since I do my compiling on the command line that will probably get a bit annoying, but I'll probably just make a custom command to handle it. Thanks again =D — Jonathan McDevitt, Jun 11 '16 at 17:54

C# Utility Class - Setting up for General Use and Compiling w/o Main

2 Answers2