Using Namespaces in Different Projects in C#

Question

I am confused on how to use a namespace. I understand that a namespace is a way to group a variety of different classes into one section. My problem is I don't understand how to use such a namespace.

For example lets say I create

using System;

namespace MyMath
{
     static class MyOperations
     {
           public static int MyAdd(int x, int y)
           {
                return x + y;
           }
     }
}

This is created in a seperate project in C#.

Now what if I want to use this namespace in a different project to use my method how do I go about doing that?

using System;
using MyMath;

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
             int sum = MyOperations.Add(5, 10);
        }
    }
}

This will give me an error. I don't understand where I put the Program.cs of the MyMath project to make it useable in the other project.

Answer 1

There are two things you have to do:

1. Add a reference to MyMath's dll.
2. The MyOperations class should have a public access modifier. Right now, it has internal ; that means, you can use the class only in the same assembly it is declared in. Change it to the following: public static class MyOperations

Answer 2

You need to add a project reference in your console project to your class library project.

See https://msdn.microsoft.com/en-us/library/f3st0d45.aspx?f=255&mspperror=-2147217396#Anchor_1

Answer 3

You have two options. Suppose MyMath is a Main Namespace where you will add Test Namespace

If you use different project in same Solution Explorer then you need to add source project from Add Reference->Project then select.

If you use different project in different Solution Explorer then you need to add dll of Source(Test Namespace) project from Add Reference.

We can use Test Namespace

using Test;