[c#] C# importing class into another class doesn't work

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.

I know this is very old question but I had the same requirement and just discovered that after c#6 you can use static in using for classes to import.

I hope this helps someone....

using static yourNameSpace.YourClass;

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

    public class MyClass
    {
        void Stuff()
        {

        }
    }
}

You have no need for using a namespace then because it is all encompased in the same namespace.

If you are unsure of what namespace your class is located, type the class (case sensitive you wish to use) then with your cursor on the class, use CTRL + . and it will offer you a manual import.

Well what you have to "import" (use) is the namespace of MyClass not the class name itself. If both classes are in the same namespace, you don't have to "import" it.

Definition MyClass.cs

namespace Ns1
{
    public class MyClass
    {
        ...
    }
}

Usage AnotherClass.cs

using Ns1;

namespace AnotherNs
{
    public class AnotherClass
    {
        public AnotherClass()
        {
            var myInst = new MyClass();
        }
    }
}

If the other class is compiled as a library (i.e. a dll) and this is how you want it, you should add a reference from visual studio, browse and point to to the dll file.

If what you want is to incorporate the OtherClassFile.cs into your project, and the namespace is already identical, you can:

1. Close your solution,

2. Open YourProjectName.csproj file, and look for this section:

   <ItemGroup>                                            
       <Compile Include="ExistingClass1.cs" />                     
       <Compile Include="ExistingClass2.cs" />                                 
       ...
       <Compile Include="Properties\AssemblyInfo.cs" />     
   </ItemGroup>
   

1. Check that the .cs file that you want to add is in the project folder (same folder as all the existing classes in the solution).

2. Add an entry inside as below, save and open the project.

   <Compile Include="OtherClassFile.cs" /> 
   

Your class, will now appear and behave as part of the project. No using is needed. This can be done multiple files in one shot.

MyClass is a class not a namespace. So this code is wrong:

using MyClass //THIS CODE IS NOT CORRECT

You should check the namespace of the MyClass (e.g: MyNamespace). Then call it in a proper way:

MyNamespace.MyClass myClass =new MyNamespace.MyClass();

using is used for importing namespaces not classes.

So if your class is in namespace X

namespace X
{
    public class MyClass {
         void stuff() {

         }
    }
}

then to use it in another namespace where you want it

using System;
using X;

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

If they are separate class files within the same project, then you do not need to have an 'import' statement. Just use the class straight off. If the files are in separate projects, you need to add a reference to the project first before you can use an 'import' statement on it.