What are .NET Core and ASP.NET Core?

Before trying to understand the reason for its existence, let's first try to define what .NET Core and ASP.NET Core are.

.NET Core

The framework .NET Core 1.1 a is modular, cross-platform, cloud-optimized version of the .NET Framework, consisting of the CoreCLR and the implementation of the .NET Standard Library 1.6. One of the main features of this library is the ability to install only the features that are needed for the application you are building, reducing its footprint and the possibility of installing the library itself within the application. This makes it possible for applications built with different versions to co-exist on the same machine without the compatibility problems typical of the full .NET Framework.

ASP.NET Core

ASP.NET Core is a complete rewrite of ASP.NET, built with the goal of being cross-platform, completely open-source, and without the limitations of backward compatibility. Like .NET Core, ASP.NET Core is also built with a modular approach. This means the application you build can include only the needed features without taking on additional burdens. This is made possible by the new startup and execution environment, based on the Open Web Interface for .NET (OWIN) standard. In addition, ASP.NET Core comes with many interesting features that we are going to see throughout the book, like an integrated dependency injection system and a new application framework that unifies the programming models of ASP.NET MVC and Web API.