Microsoft Open Sources .NET

Microsoft is now open sourcing the very foundation of .NET - the software that millions of developers use to build and operate websites and other large online applications. Sacha Bruttin unwraps this early Christmas present. Warning: contains technical language!


On November 12 & 13, Microsoft held a developer event in New York City called Connect();  As a seasoned .NET developer, I expected to hear about the next release of Visual Studio and of the .NET framework. However, during the opening keynote, Scott Guthrie, Executive Vice President of the Cloud and Enterprise group at Microsoft announced some breaking news for the .NET ecosystem.

Open Sourcing .NET

Yes, the Core Runtime and libraries of .NET are now Open Source. You might be thinking, “Yes, that is purely hype, they will never commit to it. And if they do, they will use restrictive licensing not considered as ‘Open’…” Well in fact, you’re wrong.

Firstly, the Core Runtime includes everything needed to execute .NET code (including the CLR, JIT Compiler, Garbage Collector, and core .NET base case libraries). This code is released under the MIT open source license and are also issuing an explicit patent promise to clarify user patents rights to .NET. Last but not least, everything is published to a public repository on GitHub.

Wahoo…! That’s huge. But wait…

Microsoft has a new lover

In fact, he has two new lovers, Linux and OS X. Linux is already a first-class citizen on Microsoft Azure where more than 20% of the VMs are based on the open OS. There are five Linux distributions officially supported and fully integrated with the management portal. 

But today, it is .NET that is coming to Linux and OS X. It was already possible to run .NET application on these platforms using Mono, but now you have an official Microsoft stamp on it.

During the same event, Microsoft announced the next versions of .NET and Visual Studio. ASP.NET 5 will be available for Windows, Mac and Linux which is great. Moreover, it will include a web server specifically developed for these 2 environments. It is called kestrel and it is built on libuv. It is similar to the one that come with node, and you could front it with Nginx for production, for example.

Cool, but do you have an IDE (Integrated Development Environment) for me?

No problem, Visual Studio 2015 and ASP.NET will support gulp.js, Grunt, Bower and npm for front end developers. Moreover, a new edition of Visual Studio is coming, called Visual Studio Community 2013 and is a fully-featured edition that allows developers to target any platform, from desktop and mobile to web and cloud. Most importantly, it is free for any non-enterprise application development.

My needs are more mobile

Ok, Visual Studio 2015 is for you. It offers the most complete cross-platform mobile development environment. Not only for C# and C++, but also for HTML/JS development. All of this, targeting iOS, Android, Windows and more.

If you are versed on HTML/JS for your cross-platform development, you certainly use Apache Cordova. The Visual Studio support for Codova provides tools for authoring, debugging, analyzing, packaging, and deploying application all within the IDE.

If you’re an Android developer, you certainly suffer from the poor Android Emulator proposed by Google with the SDK. Welcome to the Visual Studio Emulator for Android, a high-performance x86 based emulator that support a variety of productivity features for emulating device inputs like accelerometer, location, and network conditions.


There were a lot of other announcements during this event, available on Channel9. These announcements support the new Microsoft strategy “Mobile First, Cloud First”. Which platform is no longer a question with Microsoft - you can use your preferred OS with your language of choice. And then deploy on Microsoft Azure…

Sacha Bruttin is Lead Consultant, Microsoft Solutions at blue-infinity

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About the author

Sacha Bruttin
Sacha Bruttin

I have a strong technical expertise on the Microsoft .Net technologies area with experience on developing back-end services and also front-end applications using either web interface or windows UI.