Introduction to .NET Core

.NET Core is a cross-platform open-source managed software framework. It is built on top of CoreCLR, a complete cross-platform runtime implementation of CLR.

.NET Core applications can be developed, tested, and deployed on cross platforms such as Windows, Linux flavors, and macOS systems.

.NET Core has the following important components:

• CoreCLR: This is the .NET Core execution engine which performs the essential tasks of GC, compilation to machine code.
• CoreFX: This contains class libraries for collections, filesystem, XML, async, and so on for .NET Core.
• SDK Tools: This is a set of SDK tools for day-to-day development experience. Creating projects, build, run, and tests are common developer needs that are part of these SDK tools.

.NET Core shares a subset of the original .NET Framework, plus it comes with its own set of APIs that is not part of the .NET Framework. This results in some shared APIs that can be used by both .NET Core and the .NET Framework.

A .Net Core application can easily work on the existing .NET Framework, but not vice versa.

.NET Core provides a CLI (Command Line Interface) for an execution entry point for operating systems, and provides developer services such as compilation and package management.

The following are some interesting points to know about .NET Core:

• .NET Core can be installed on cross platforms like Windows, Linux, and macOS. It can be used in device, cloud, and embedded/IoT scenarios.
• Visual Studio IDE is not mandatory to work with .NET Core, but when working on the Windows OS, we can leverage the existing IDE knowledge.
• .NET Core is modular, which means that, instead of assemblies, developers deal with NuGet packages.
• .NET Core relies on its package manager to receive updates, because cross-platform technology can't rely on Windows updates.
• To learn .NET Core, we just need a shell, text editor, and it's runtime installed.
• .NET Core comes with flexible deployment. It can be included in your app or installed side-by-side user- or machine-wide.
• .NET Core apps can also be self-hosted/run as standalone apps.

.NET Core supports four cross-platform scenarios: ASP.NET Core web apps, command-line apps, libraries, and Universal Windows Platform apps.

It does not support Windows Forms or WPF which render the standard GUI for desktop software on Windows.

At present,only the C# programming language can be used to write .NET Core apps. F# and VB support are on the way.

We will, primarily, focus on the ASP.NET Core web apps, which include MVC and web API. CLI apps and libraries will be covered briefly. As its cross platform, having to install Visual Studio IDE to create applications is not mandatory. In this section, we will install .NET Core, build very a basic .NET Core application, and learn about the different commands for .NET Core.