.NET Core

.NET Core is a modular version of the .NET Framework designed to be portable across platforms for maximum code reuse and code sharing. In addition, .NET Core will be open-sourced and accept contributions from the community.

What is .NET Core?

.NET Core is portable across platforms because, although a subset of the full .NET Framework, it provides key functionality to implement the app features you need and reuse this code regardless of your platform target. In the past, different versions of .NET for different platforms lacked shared functionality for key tasks such as reading local files. Microsoft platforms that you will be able to target with .NET Core include traditional desktop Windows, as well as Windows devices and phones. When used third-party tools such as Xamarin, .NET Core should be portable to IOS and Android devices. In addition, .NET Core will soon be available for the Mac and Linux operating systems to enable web apps to run on those systems.

.NET Core is modular because it is released through NuGet in smaller assembly packages. Rather than one large assembly that contains most of the core functionality, .NET Core is made available as smaller feature-centric packages. This enables a more agile development model for us and allows you to pick and choose the functionality pieces that you need for your apps and libraries. For more information about .NET packages that release on NuGet, see, The .NET Framework and Out-of-Band Releases.

For existing apps, using Portable Class Libraries (PCL), Universal app projects and separating business logic from platform specific code is the best way to take advantage of .NET Core, and maximize your code reuse. For apps, Model-View-Controller (MVC) or the Model View-ViewModel (MVVM) patterns are good choices to make your apps easy to migrate to .NET Core.

In addition to the modularization of the .NET Framework, Microsoft is open-sourcing the .NET Core packages on GitHub, under the MIT license. This means you can clone the Git repo, read and compile the code and submit pull requests just like any other open source package you might find on GitHub.

.NET Core 5 is a modular runtime and library implementation that includes a subset of the .NET Framework. Currently it is feature complete on Windows, and in-progress builds exist for both Linux and OS X. .NET Core consists of a set of libraries, called “CoreFX”, and a small, optimized runtime, called “CoreCLR”. .NET Core is open-source, so you can follow progress on the project and contribute to it on GitHub:

• .NET Core Libraries (CoreFX)
• .NET Core Common Language Runtime (CoreCLR)

The CoreCLR runtime (Microsoft.CoreCLR) and CoreFX libraries are distributed via NuGet. The CoreFX libraries are factored as individual NuGet packages according to functionality, named “System.[module]” on nuget.org.

One of the key benefits of .NET Core is its portability. You can package and deploy the CoreCLR with your application, eliminating your application’s dependency on an installed version of .NET (e.g. .NET Framework on Windows). You can host multiple applications side-by-side using different versions of the CoreCLR, and upgrade them individually, rather than being forced to upgrade all of them simultaneously.

CoreFX has been built as a componentized set of libraries, each requiring the minimum set of library dependencies (e.g. System.Collections only depends on System.Runtime, not System.Xml). This approach enables minimal distributions of CoreFX libraries (just the ones you need) within an application, alongside CoreCLR. CoreFX includes collections, console access, diagnostics, IO, LINQ, JSON, XML, and regular expression support, just to name a few libraries. Another benefit of CoreFX is that it allows developers to target a single common set of libraries that are supported by multiple platforms.