From steps 1 to 4, we created a blank solution using Visual Studio 2017 and gave it a location and a proper meaningful name. Then, from steps 5 to 9, we added a new .NET Standard 2.0 library to the blank solution. As usual, we gave it a proper and meaningful name.
In steps 12 and 13, we renamed the default Class1.cs template to TelephoneBook.cs. It's a good practice to keep both the class and filename the same. This is more readable and understandable when you come back to your code. In step 16, we added two namespaces to the code. System.Collections.Generic will get you the List<T> class used in the code and System.Linq gives you more control over those generic collections by allowing the LINQ functionality.
In step 17, ...
