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The corefx repo contains the library implementation (called "CoreFX") for .NET Core. It includes System.Collections, System.IO, System.Xml and many other components. You can see more information in Documentation.

.NET Core is a modular implementation of .NET that can be used as the base stack for a wide variety of scenarios, today scaling from console utilities to web apps in the cloud. You can learn more about .NET Core and how and where you can use it in the .NET Core is open source and Introducing .NET Core blog posts. The .NET Core Roadmap describes where the team is headed.

The .NET Core Runtime repo contains the runtime implementation (called "CoreCLR") for .NET Core. It includes RyuJIT, the .NET GC, native interop and many other components.

Runtime-specific library code - namely mscorlib - lives in the CoreCLR repo. It needs to be built and versioned in tandem with the runtime. The rest of CoreFX is agnostic of runtime-implementation and can be run on any compatible .NET runtime. These characteristics were the primary motivation for the 2-repo structure.

Some of the best ways to contribute are to try things out, file bugs, and join in design conversations. If you are having issues with the Full .NET Framework or .NET Runtime, the best way to file a bug is at Connect or through Product Support if you have a contract.

Want to get more familiar with what's going on in the code?

• Pull requests: Open/Closed
• , and changes

Looking for something to work on? The list of up-for-grabs issues is a great place to start. See some of our guides for more details:

• Contributing Guide
• Developer Guide
• Issue Guide

We've also started to share some of our direction via more higher-level documentation, specifically:

• Road to RTM
• How we triage
• Porting to .NET Core

You are also encouraged to start a discussion by filing an issue or creating a gist.

You can discuss .NET OSS more generally in the .NET Foundation forums.

Want to chat with other members of the CoreFX community?

The repo contains the source for each of the assemblies that comprises .NET Core. Each Microsoft.* or System. folder under src represents an individual library. Each such folder may contain a ref folder, which contains the source representing the "contract" or "reference assembly" for that library. It may also contain a src folder, which contains the source for some or all of the implementation for that library (some implementation may live in mscorlib in the coreclr repo, with the build tooling generating type forwards from the library assembly to mscorlib.)
It may also contain a test folder containing the tests associated with that library, whether the implementation source lives in corefx or in coreclr.

Daily builds of .NET Core components are published to dotnet-core MyGet gallery. The latest version number of each library can be seen in that gallery.

.NET Core (including the corefx repo) is licensed under the MIT license.

.NET Core is a .NET Foundation project.

There are many .NET related projects on GitHub.

• The .NET home repo links to 100s of .NET projects, from Microsoft and the community.
• The .NET Core repo links to .NET Core related projects from Microsoft.
• The ASP.NET home repo is the best place to start learning about ASP.NET 5.
• dotnet.github.io is a good place to discover .NET Foundation projects.