Visual Studio .NET 2003 C# Compile Error CS0042

I am working on a VS.NET 2003 C# web project that contains multiple projects and on occasion I get an annoying fatal build error (CS0042):

Unexpected error creating debug information file ‘<project path>\obj\Debug\<DLL Name>.PDB’: The process cannot access the file because it is being used by another process.

Starting with a Google search led me to many developers having the same or similar problems with the following advice:

1. Exit VS.NET, restart VS.NET and reopen project
2. Change project from Debug Build to Release Build and visa-versa.
3. Remove all Enums from classes and just use in the namespace
4. Ensure all DLL projects have  ‘CopyLocal’ set to true AND references to these DLL’s be a Project Reference and not simple a DLL reference.

I followed all of the guidance of the experiences I saw in my Google search with #1 working every time.  The only problem with this solution was exiting and restarting VS.NET all the time.  In case you haven’t had the pleasure, it takes a long time to load.  Although this worked, it didn’t seem the greatest solution to me and was a poor way to fix a deeper problem.

Further sluething using Process Explorer from Sysinternals revealed Devenv.exe was holding my PDB file open.  A post to the MSDN .NET General Newsgroup let to some further clues.

As I pointed out, I am not the only one having this problem, and it seems Microsoft is well aware of these issues.  KnowledgeBase articles 313512 and 887818 show occurances of the bug and a hotfix that is available by request-only.  I don’t think this is the right approach to such an annoying problem and either does Frans Bouma who has a great post on his blog about this very problem and the lack of service pack for VS.NET 2003.

I called Microsoft to request this hotfix and the person I spoke with fromt he VS.NET 2003 C# Support Team told me I was the third person requesting this hotfix THIS MORNING.  So, why don’t we see a service pack before now? We have seen multiple hotfixes for Windows XP already and VS.NET 2003 has been in use just as long.  If I recall correctly we had six service packs for Visual Studio 6.

I have installed the hotfix and all seems to be working well with no problems reported.  I hope this helps others out there.