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I am unable to add an existing project or an existing item to any project or solution in visual studio 2008 (SP1). I only get an "Operation cannot be completed error".

Any ideas?

Things I have tried that did not work:

  • ran devenv /resetsettings (no luck)
  • Un-installed Resharper 4.5. (no luck)
  • Repaired Visual Studio from Add/Remove Programs. (no luck)
  • Un-installed AnkhSVN. (no luck)

Note I am using Windows 7.

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Are you able to open the existing project or item separately in vs2008? How you tried adding the project or items to a newly created solution? – mindless.panda Mar 4 '10 at 15:27
You can run devenv.exe in safemode, which might give additional hints: devenv.exe /safemode – Bobby Mar 5 '10 at 8:57
Good idea, Bobby. But I'm afraid VS still fails and it does not give any extra info :( – willem Mar 8 '10 at 7:03

You should be able to blow away the .sln file, and re-create it, then add your existing projects to the new one.

I've had good success editing them by hand, so perhaps you can open it up in a text editor and take a look.

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Unfortunately hand-editing the file is the only thing that has worked so far. – willem Mar 8 '10 at 7:03

Check to make sure the project and solution files are not marked as read only.

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Good idea. But none of my files are marked as read only. So no luck there. – willem Mar 4 '10 at 15:25
up vote 0 down vote accepted

I finally found a solution to this problem. I am using Windows 7, so on my VS.NET EXE's properties I turned on compatibility mode for XP SP3, and I disabled Visual Themes (for VS.NET exe specifically). I also turned off clear type fonts.

Not sure which of these changes exactly solved the problem, but VS.NET is working again.

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