Visual Studio 2012 - Can't find System.Transactions assembly in .NET 4.5 framework

Question

I'm trying to add a reference to System.Transactions in a C# Visual Studio 2012 project, but System.Transactions isn't available among the framework assemblies, as you can see for yourselves in the below screenshot:

Does anyone know why System.Transactions would be unavailable to me? How can I make it reappear?

Edit: Fixed the screenshot, thanks Marc!

Answer 1

There was a Microsoft Connect entry posted for this, which had a comment suggesting that you can browse for it. The path given is:

C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.Transactions.dll

Answer 2

install in packages NuGet... Visual Studio: Castle.Services.Transaction