C# 7 and .NET: Designing Modern Cross-platform Applications

Building class libraries

Class library assemblies group types together into easily deployable units (DLL files). Apart from when you learned about unit testing, you have only created console applications to contain your code. To make the code that you write reusable across multiple projects, you should put it in class library assemblies, just like Microsoft does.

Good Practice Put types that you might reuse in a .NET Standard class library to enable them to be reused in .NET Core, .NET Framework, and Xamarin projects.