Solved! Go to Solution.
I'm guessing your standalone is attempting to reference the old 10.1 location?
Just an idea, not sure if it is correct as I have not had to build a stand alone application for some time but in VS, in the solution Explorer panel> References
set each ESRI reference to Copy Local = TRUE. This should bundle up the DLLs into the same folder as your executable.
The problem is that when you link your application with ESRI assemblies the resulting executable will reference the exact version that you linked against. Setting the assembly reference to be non-version specific only changes what it does when it builds. This is how .NET behaves and has nothing to do with ESRI.
The way that you can make this work is to redirect your assembly references:
You can see how ESRI does this by looking at ArcMap.exe.config. You could build against 10.1 and then (assuming ESRI made no breaking API changes) provide an application configuration for your 10.2 delivery which simply redirected your 10.1 assembly references to 10.2. I have done this very thing.