Question: Probably between 25 and 50% of the times I build my solution, I see this:

"[The operation you requested is taking longer than expected to complete. This dialog will close when the action completes.](https://i.imgur.com/UOtXUud.png)"

I hate this window in ways I can't describe. It never resolves, the Cancel button is never enabled, and the only way to remedy it is to kill the devenv process and load up my entire solution again, knowing full well that I've fixed nothing and I'm equally liable to see the same thing when I attempt my build.

My solution is about 60 projects in total, which are mostly C# class libraries, with a few each of web applications, web services, and console applications. However, the problem persists even when building one slice of the codebase with the majority (50) of the projects unloaded.

My problem is that the output windows doesn't tell me anything at the point at which it freezes, and I don't know how else to determine the cause of this lockup. If I were to guess, I would assume that it's a deadlock in the filesystem or something, but I don't know how to go about proving this--much less how to prevent it.

What can I do to diagnose and eliminate this from my solution so that I never see it again? In general, how can I diagnose problems that occur during a build?

Answer: 
I moved my VS 2008 development platform from Windows 7 to Windows 10 and encountered a situation where Visual Studio would hang up every time I tried to build a large project. I had to build the project, then use the Task Manager to kill VS and then restart. Needless to say, this made debugging really difficult! Anyhow, the problem was that in moving to Win 10, VS was no longer running as administrator (and perhaps Win 10 is more particular about privileges). Changing the properties so that the program ran as administrator resolved the problem. (IngoB -- I don't have enough status to comment on your post, but thanks for pointing this out!)
I had this problem because of an issue restoring nuget packages. There was a duplicate entry in the `packages.config` file. Rather than report it as an error, the build would just hang forever.

I didn't discover the problem until I tried to restore the nuget package through the "Manage Nuget Packages..." option in the menu. After removing the duplicate, the build completes properly.