At its Build 2014 conference today, Microsoft announced it is open sourcing its .NET compiler platform “Roslyn” – and then did exactly that, live on stage. Microsoft’s Anders Hejlsberg hit the button to make the project public on Codeplex.

For those who don’t know, Roslyn is a set of APIs for exposing the Microsoft C# and Visual Basic .NET compilers as services available at runtime. It includes versions of the C# and VB.NET compilers written in the languages themselves; in other words, the compilers are available via the traditional command-line programs, as well as APIs available natively from within .NET code.

Roslyn is integrated in the latest version of Visual Studio. A developer preview was first released back in October 2011.


Scott Guthrie, Executive Vice President of Cloud and Enterprise, announced the decision today is part of a broader initiative called .NET Foundation, the company’s move to open source multiple .NET components. There are 24 .NET open source projects to start, most of which are under the Apache 2.0 license.

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