Question

I’m quite new to C#, and have made a class that I would like to use in my main class. These two classes are in different files, but when I try to import one into the other with using, cmd says says

The type or namespace name “MyClass” could not be found (are you missing a using directive or an assembly reference?

I know that in Java I have to mess around with CLASSPATH to get things like this to work, but I have no idea about C#.

Additional details:

As you’ve probably figured out, I’m compiling and executing via command prompt. I’m compiling my non-main class using /target:library (I heard that only main classes should be .exe-files).

My code looks like this:

public class MyClass {
    void stuff() {

    }
}

and my main class:

using System;
using MyClass;

public class MyMainClass {
    static void Main() {
        MyClass test = new MyClass();
        /* Doesn't work */
    }
}

I have tried to encompass my non-main class with namespace MyNamespace { } and importing that, but it doesn’t work either.

Answer 1

UPDATE: As of C# 6, if you want to use the static members of a class without specifying the class name, you can use the using static directive to import the static members into the current scope, like this:

using static MyNamespace.MyClass;

Although this is not what the original question is about, you get a similar error to the one OP gets, so I’m providing it for completeness.

Answer to OP’s question:

using is for namespaces only – if both classes are in the same namespace just drop the using.

You have to reference the assembly created in the first step when you compile the .exe:

csc /t:library /out:MyClass.dll MyClass.cs
csc /reference:MyClass.dll /t:exe /out:MyProgram.exe MyMainClass.cs

You can make things simpler if you just compile the files together:

csc /t:exe /out:MyProgram.exe MyMainClass.cs MyClass.cs

or

csc /t:exe /out:MyProgram.exe *.cs

EDIT:
Here’s how the files should look like:

MyClass.cs:

namespace MyNamespace {
    public class MyClass {
        void stuff() {
 
        }
    }
}

MyMainClass.cs:

using System;

namespace MyNamespace {
    public class MyMainClass {
        static void Main() {
            MyClass test = new MyClass();
        }
    }
}