When adding a DLL as a reference to an ASP.Net project, VS2008 adds several files to the bin directory. If the DLL is called foo.dll, VS2008 adds foo.dll.refresh, foo.pdb and foo.xml. I know what foo.dll is :-), why does VS2008 add the other three files? What do those three files do? Can I delete them? Do they need to be added in source control?
The pdb is there for debugging and symbols. If you get an exception thrown from it, you'll be able to get stacktraces, etc. You're in control of choosing whether or not the PDB is built. The xml file is there for XML comments and intellisense. Visual Studio will parse that and display the XML comments that were added when you call methods in those DLLs.
I don't know about the refresh file.
foo.pdb is the debugger symbols file for foo.dll, you'll want it or you won't be able to set a breakpoint in that code.