Exception from HRESULT: 0x80131047

If you are using Assembly.Load() to load file try to change it with Assembly.LoadFile() instead.

It may not necessarily be related to that as in my case...

First, I would like to say that this was a very hard issue troubleshoot as there may be many variables leading to the actual problem related to assemblies.

So I was working on an Outlook Add-In 2010 targeting the 32-bit version of Office. Everything was working fine until one day out of the blues, the add-in wouldn't load anymore and I was presented with error "HRESULT: 0x80131047". After searching almost half a day I found a nice article:

http://blogs.msdn.com/b/astebner/archive/2007/05/06/2457576.aspx

I tried adding the assembly to the global cache but was unable to. Luckily, I had an almost identical project which ran just fine and I had already done comparison checks and everything seemed the same, but on this pass I found something different ... as it turned out the platform target CPU was set to 64-bit so I changed it to "Any" and voila'! - this fixed it!

Project > Project Properties > Name > remove the apostrophe ("'") from the name, and it will work.