How it works...

From steps 1 to 4, we created a blank solution. Then, from steps 5 to 9, we added a .NET Standard 2.0 library to the blank solution. In step 12, we renamed the existing Class1.cs that came with the template to something more meaningful. We also renamed the class name to match the filename. This is good practice and is also the default behavior of Visual Studio when you create a brand new class. We changed the name to Calculator.cs and the class name to Calculator. 

In step 14, we added two simple methods to the Calculator class. The first method adds the given integers and the second method subtracts one integer from another. Finally, we did a quick build to check for syntax errors.