Build fails on mapped drive, but not locally

Question

I'm working on a game written in C# using VS2013 and monogame. However, monogame doesn't support the XNA content pipeline (still), so the going advice is to build your content separately using Microsoft's XNA and VS2010. Since I didn't want to clutter my primary development machine (Win8) with VS2010 et cetera, I created a Win7 virtual machine to run Win7 along with VS2010 and all the tooling I need to build my content. All my project and solution files have corresponding 2010 versions, and the 2010 solution only has the necessary projects to build the content.

I can successfully build the content, but only if it's present direcly on the VM's hard disk (C:\). If I map a local drive to a network share on the host machine and attempt to build, I get a build time error. Why do I want to do this? Because I want a single copy of the source tree so I can iterate at a decent speed. It's just far too painful and error-prone if I have a separate source tree in the VM.

Here's the build error I get:

Error loading pipeline assembly "S:\Src\ContentPipelineExtension\bin\x86\Debug\Newtonsoft.Json.dll".

I have S:\ mapped to my network share. Newtonsoft.Json.dll exists at the indicated path.

I have tried:

• specifying /verbosity:d when building to see if any more information is output. There isn't.
• attaching a debugger to the MSBuild.exe process with break on any exception enabled. It never breaks.
• using subst instead of Windows Explorer's drive mapping tool (it might be using subst behind the scenes, but I wanted to be sure).
• debugging MSBuild, but I hit the "mismatched leave" bug when I did so.
• applied the workaround for the mismatched leave bug and debugged the build simultaneously on both C:\ and S:\. In both cases, I put a breakpoint right before XNA's BuildContent task was called. I let both builds run until they hit this breakpoint, and then I opened the locals windows, side-by-side. I compared all locals and found no difference apart from the expected C:\ versus S:\ path roots.
• spelunking through the XNA code in ILSpy to try and figure out where it's going wrong, but have had no luck with that either
• enabling full trust on the network share in CAS by executing: CasPol.exe -m -ag 1.2 -url file://S:\* FullTrust. No change in behavior.
• enabling Fusion Log Viewer (fuslogvw.exe) and checking out its log. It says it has successfully loaded the assembly!
• added <loadFromRemoteSources enabled="true"/> to my MSBuild.exe.config. No change.

Why does the build fail when running off my mapped S:\ and succeed when a copy of the source is placed on my C:\?

UPDATE: I just found the most awful work-around. I modified my ContentPipelineExtension project's Output Path such that it is an absolute directory on my C:\. This allows the build to complete successfullly, but is obviously far from ideal.

Answer 1

Here is a hack I used. It's not a satisfying answer (and I won't mark it as accepted), but in the absence of a better solution, it will save me an enormous amount of time and pain.

I edited my 2010 project files and changed my output paths to something like this:

<OutputPath>$(TEMP)\ContentPipelineExtension\bin\x86\Debug\</OutputPath>

The TEMP environment variable resolves to a folder on C:\ and saves me hard-coding a specific path. Now I can build the project from my Win7 VM using the same source tree as I use in my primary Win8 machine.