I’ve just been asked through the “Ask” widget on the side of this blog on Yedda (my day job) this question:

Yedda � People. Sharing. Knowledge.Where is sos.dll for .net 3.5?

I installed Visual Studio 2008, but I don’t see sos.dll in the Microsoft.NET\Framework\v3.5 directory? What’s up with that?

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Asked by dannyR on January 03, 2008

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To which I replied:

Yedda � People. Sharing. Knowledge.Where is sos.dll for .net 3.5?

There is a bit of confusion as to the .NET Framework versions as opposed to the CLR (Common Language Runtime) versions.

Up until .NET Framework 2.0, the CLR versions advanced side by side with the versions of the framework.

Starting from .NET Framework v3.0, the version of the CLR stated at 2.0 (there was no significant change in the CLR itself) and the framework’s version kept on going forward.

.NET Framework v3.5 actually runs on CLR 2.0 SP1.

This means that you can should be able to use the SOS.dll located at Microsoft.NET\Framework\v2.0.50727 with either Visual Studio (as I’ve explained on this post) or with WinDbg.

Dave Broman of Microsoft has written a post about the mapping of the versions of the .NET Framework to the version of the CLR. Do mind that as Dave states in his post, its the way he figures things up in his head and not the official documentation on this matter.

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Answered by Eran on January 03, 2008

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I know its a bit confusing and I’m not really sure why Microsoft detached the versions of the Framework from the versions of CLR (well, I can understand some of the thoughts leading to this but I don’t think it was that good of a move) but Dave’s excellent post does put things in perspective and allows figuring out in what version of the CLR you are actually using.