.NET Core an Open Source Framework

This topic provides a brief overview of what .NET Core is and shows how you can find more information

What is .NET Core?

.NET Core is a general purpose, modular, cross-platform and open source implementation of the .NET Standard. It contains many of the same APIs as the .NET Framework (but .NET Core is a smaller set) and includes runtime, framework, compiler and tools components that support a variety of operating systems and chip targets. The .NET Core implementation was primarily driven by the ASP.NET Core workloads but also by the need and desire to have a more modern implementation. It can be used in device, cloud and embedded/IoT scenarios.

Here are the main characteristics of .NET Core:1

  • Cross-platform: .NET Core provides key functionality to implement the app features you need and reuse this code regardless of your platform target. It currently supports three main operating systems (OS): Windows, Linux, and macOS. You can write apps and libraries that run unmodified across supported operating systems. To see the list of supported operating systems, visit .NET Core roadmap.
  • Open source: .NET Core is one of the many projects under the stewardship of the .NET Foundation and is available on GitHub. Having .NET Core as an open source project promotes a more transparent development process and promotes an active and engaged community.
  • Flexible deployment: there are two main ways to deploy your app: framework-dependent deployment or self-contained deployment. With framework-dependent deployment, only your app and third-party dependencies are installed and your app depends on a system-wide version of .NET Core to be present. With self-contained deployment, the .NET Core version used to build your application is also deployed along with your app and third-party dependencies and can run side-by-side with other versions. For more information, see .NET Core Application Deployment.
  • Modular: .NET Core is modular because it’s 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 optimize your app to include just the NuGet packages you need. The benefits of a smaller app surface area include tighter security, reduced servicing, improved performance, and decreased costs in a pay-for-what-you-use model.


.NET Core is composed of the following parts:

  • .NET runtime, which provides a type system, assembly loading, a garbage collector, native interop and other basic services.
  • A set of framework libraries, which provide primitive data types, app composition types and fundamental utilities.
  • set of SDK tools and language compilers that enable the base developer experience, available in the .NET Core SDK.
  • The ‘dotnet’ app host, which is used to launch .NET Core apps. It selects the runtime and hosts the runtime, provides an assembly loading policy and launches the app. The same host is also used to launch SDK tools in much the same way.


The C#, Visual Basic, and F# languages can be used to write applications and libraries for .NET Core. The compilers run on .NET Core, enabling you to develop for .NET Core anywhere it runs. In general, you will not use the compilers directly, but indirectly using the SDK tools.

The C#, Visual Basic, and F# compilers and the .NET Core tools are or can be integrated into several text editors and IDEs, including Visual Studio, Visual Studio Code, Sublime Text and Vim, making .NET Core development an option in your favorite coding environment and OS. This integration is provided, in part, by the good folks of the OmniSharp project.

.NET APIs and Compatibility

.NET Core can be thought of as a cross-platform version of the .NET Framework, at the layer of the .NET Framework Base Class Libraries (BCL). It implements the .NET Standard specification. .NET Core provides a subset of the APIs that are available in the .NET Framework or Mono/Xamarin. In some cases, types are not fully implemented (some members are not available or have been moved).

Look at the .NET Core roadmap to learn more about the .NET Core API roadmap.

Relationship to .NET Standard

The .NET Standard is an API spec that describes the consistent set of .NET APIs that developers can expect in each .NET implementation. .NET implementations need to implement this spec in order to be considered .NET Standard-compliant and to support libraries that target .NET Standard.

.NET Core implements .NET Standard, and therefore supports .NET Standard libraries.


By itself, .NET Core includes a single application model — console apps — which is useful for tools, local services and text-based games. Additional application models have been built on top of .NET Core to extend its functionality, such as:

Open Source

.NET Core is open source (MIT license) and was contributed to the .NET Foundation by Microsoft in 2014. It is now one of the most active .NET Foundation projects. It can be freely adopted by individuals and companies, including for personal, academic or commercial purposes. Multiple companies use .NET Core as part of apps, tools, new platforms and hosting services. Some of these companies make significant contributions to .NET Core on GitHub and provide guidance on the product direction as part of the .NET Foundation Technical Steering Group.

Comparisons to other .NET implementations

It is perhaps easiest to understand the size and shape of .NET Core by comparing it to existing .NET implementations.

Comparison with .NET Framework

.NET was first announced by Microsoft in 2000 and then evolved from there. The .NET Framework has been the primary .NET implementation produced by Microsoft during that 15+ year span.

The major differences between .NET Core and the .NET Framework:

  • App-models — .NET Core does not support all the .NET Framework app-models, in part because many of them are built on Windows technologies, such as WPF (built on top of DirectX). The console and ASP.NET Core app-models are supported by both .NET Core and .NET Framework.
  • APIs — .NET Core contains many of the same, but fewer, APIs as the .NET Framework, and with a different factoring (assembly names are different; type shape differs in key cases). These differences currently typically require changes to port source to .NET Core. .NET Core implements the .NET Standard API, which will grow to include more of the .NET Framework BCL API over time.
  • Subsystems — .NET Core implements a subset of the subsystems in the .NET Framework, with the goal of a simpler implementation and programming model. For example, Code Access Security (CAS) is not supported, while reflection is supported.
  • Platforms — The .NET Framework supports Windows and Windows Server while .NET Core also supports macOS and Linux.
  • Open Source — .NET Core is open source, while a read-only subset of the .NET Framework is open source.

While .NET Core is unique and has significant differences to the .NET Framework and other .NET implementations, it is straightforward to share code, using either source or binary sharing techniques.


In this article, we have learned about .net core framework. So let’s kickstart building the project using the boilerplate of the .net core in next article.

  • Facebook
  • Twitter
  • Google+
  • Linkedin
  • Pinterest


  1. I was wondering if you ever considered changing the structure of your
    site? Its very well written; I love what youve got to say.
    But maybe you could a little more in the way of content so people could connect with it better.
    Youve got an awful lot of text for only having one or 2 pictures.
    Maybe you could space it out better?

Leave a Comment

Your email address will not be published. Required fields are marked *

It is main inner container footer text