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InfoQ Homepage News Microsoft Open Sources .NET, Adds Linux and Mac OS X Support

Microsoft Open Sources .NET, Adds Linux and Mac OS X Support


The centerpiece of Microsoft’s Windows-based server application stack is going to become fully open source according to an announcement by the company today.  The .NET Core stack will now be supported on Windows, Linux, and Mac OS X.  This release of this software under an open source license joins the previously released .NET centric software: the ASP.NET stack and C# compiler (Roslyn). 

The .NET Core project now has its source code available on GitHub, providing the key foundational libraries for the following components, all of which are licensed under the MIT open source license:

  • Immutable Collections. A set of collection types that make it easy to keep mutable state under control without sacrificing performance or memory footprint. You can read more about them on MSDN.
  • ECMA-335 Metadata Reader. This is a highly tuned low-level metadata reader that allows Roslyn to parse assemblies.
  • SIMD enabled vector types. We've recently added a set of basic vector types that leverage single instruction, multiple data (SIMD) CPU instructions. See our recent announcement for more details.
  • XML. This includes the DOM APIs such as the XDocument and XmlDocument types, XLinq as well the corresponding XPath extension methods.

Microsoft’s Immo Landwerth stated that the firm’s key motivations behind the move to opening up the code base for .NET is due to a desire to improve the cross-platform support, and to improve the overall quality of the software supporting .NET.  Landwerth says that Microsoft thinks having one unified open source stack will do well to facilitate this (as opposed to the previous situation of a closed-source .NET and the independently developed Mono project).

Having an open and transparent development process means that Landwerth and his team can more easily communicate with developers as to Microsoft’s plans for the project and the reasoning behind its design decisions.  A welcome change for this project is that Landwerth is committed to avoiding “code bombs”, the process by development happens on Microsoft’s internal servers and then is periodically released en masse to public Git servers.  This obscures the development process and frequently leads to an opaque and incomplete change log. 

Landwerth says that the GitHub repository will be his team’s primary code storage system.  This transparency will also provide non-Microsoft developers with access to the project’s Code Review process for incorporating changes and the design documents used by the development team.

As part of this process, Microsoft has also released the class libraries for the .NET Framework that ships with Windows.  Miguel de Icaza of Mono says his team will be using this code to address areas of the Mono codebase that is incomplete or containing errors.  Mono’s implementation will continue to be developed independently as Microsoft must closely monitor the framework’s development for Windows to ensure that backwards compatibility is maintained.

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Community comments

  • A good step forward!

    by Cameron Purdy,

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    This is pretty cool, and long overdue!

    What I can't quite figure out from this is how much of .NET is actually being released. It may be that I'm just thick, but it still sounds like only bits and pieces are being open-sourced. (That is still positive, but it would be great to understand the scope!)


    Cameron Purdy | Oracle
    The above are solely personal opinions, and do not necessarily reflect on the views or positions of my employer.

  • Exciting News - wonder how the market looks in 36 months...

    by Michael Kramer,

    Your message is awaiting moderation. Thank you for participating in the discussion.

    Interesting how Microsoft with Satya Nadella as captain seems to depart from the vision of Windows OS as the core platform for all software. I therefore wonder what becomes of Microsoft and its products+services in the future...

    Will the open source community embrace Microsoft's offers?
    Will significant shares of Java development turn to .NET instead of Java/Scala?
    Will .NET become a major platform for software development on iOS, Android, Linux, or on the web?

    What role will Microsoft reach in the IoT market?
    What will become of "version licensed" software?
    What market shares will Microsoft Azure reach? Office 365? VS Online?

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