The easiest way to use C# protocol buffers in your project is to use the [Google.ProtocolBuffers NuGet package](http://www.nuget.org/packages/Google.ProtocolBuffers/). This package is the legacy package for C# protocol buffers, but it will work fine with C# code generated by `protoc` if you use proto2 syntax (The API of the runtime library haven't changed so far).
We will definitely release a new NuGet package for the runtime library in the future. The new runtime library WILL contain significant semantic, backwardly-incompatible changes in proto handling (mostly because we will be adding proto3 support and we will be using that oportunity to make some design changes). So keep in mind that you will need to regenerate your proto files and switch to a new NuGet package once the new version of runtime library becomes available.
Building
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Open the `src/ProtocolBuffers.sln` solution in Visual Studio. Click "Build solution" to build the solution. You should be able to run the NUnit test from Test Explorer (you might need to install NUnit Visual Studio add-in).
Supported Visual Studio versions are VS2013 (update 4) and VS2015. On Linux, you can also use Monodevelop 5.9 (older versions might work fine).