Calling class from another project

Question

I have two projects, BasicCalculator and BasicCalculator.Test.Unit. I am wanting to test classes with certain functions from the BasicCalculator project. I created a unit test file named BasicCalculator.Test.Unit and added a new reference (BasicCalculator) inside of that project.

using System;
using BasicCalculator;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace BasicCalculator.Test.Unit
{
    [TestClass]
    public class CalculatorEngineTest
    {
        private readonly CalculatorEngine _calculatorEngine = new CalculatorEngine();
        [TestMethod]
        public void TestMethod1()
        {
        }
    }
}

However, whenever I type private readonly CalculatorEngine _calculatorEngine = new CalculatorEngine(); it displays an error for CalculatorEngine which is a class in the BasicCalculator project.

It says:

class BasicCalculator.CalculatorEngine

BasicCalculator - Available
BasicCalculator.Test.Unit - Not Available

You can use the navigation bar to switch context.

The type or namespace 'CalculatorEngine' could not be found (are you missing a using directive or an assembly reference?)

Am not sure why this is occurring if I just needed to add a reference in the BasicCalculator.Test.Unit project that calls the BasicCalculator project.

ADDED INFORMATION

This is my class that I am trying to access inside of BasicCalculator.Test.Unit

using System;
using System.Collections.Generic;
using System.Text;

namespace BasicCalculator
{
    public class CalculatorEngine
    {
        public double Calculate(string argOperation, double argFirstNumber, double argSecondNumber)
        {


        }
    }
}

Solution Explorer View

Error List

Answer 1

Simply adding the project as a reference doesn't expose the project's public members to all classes in your code. You need to tell the IDE you want to link the project and use its classes with a using statement:

using BasicCalculator;

Looking at the edited question, it seems CalculatorEngine has no access modifier, meaning it has protected visibility. Classes outside of the BasicCalculator project won't be able to access it. You'll also need to make it public:

public class CalculatorEngine

---

Edit: The error list in the updated question reveals an error:

Project '..\BasicCalculator.csproj' targets 'netcoreapp3.1'. It cannot be referenced by a project that targets '.NETFramework,Version=v4.7.2'

This error is clearly stopping the BasicCalculator reference from resolving in your test project. You'll need to change the framework target in the project settings in one or the other so that they match. Or, research this error for other possible resolutions - here is a relevant SO question.

Answer 2

class CalculatorEngine should be public class CalculatorEngine to expose it to callers outside the project its declared in

you should also add using BasicCalculator; as @klaycon stated in his answer