Wierd compilation error - corrupt lines in FileList.txt

I came across a very strange error last night that flumoxed my for a while.

Compiling a solution, three of the sub projects failed to compile with the following cryptic error:

Files had invalid value "S....."

It turns out that the cause and solution are both quite simple, but neither is obvious.

Firstly, what does "Files" mean in this context?

Well, when VS2005 compiles a project, it reads a file in the obj directory named .csproj.FileList.txt, creating it first if required. This file contains a list of the DLLs and PDBs that will be generated, as well as one named ResolveAssemblyReference.cache, which (I assume) is passed to the command-line compiler used to actually perform the compilation.

As for the "invalid value", this turned out to be a corrupt line in the file, nothing more, so the solution is just to delete the obj\.csproj.FileList.txt file completely, clean the project and rebuild. Job done.

Strangely the only reference I could find to the FileList.txt file was in this posting by Sayed Ibrahim Hashimi, confirming that this is one of those undocumented "features" of VS2005.