Are you developing in ASP.NET MVC? If so, which version of the MVC? Which is the platform target of your project: x86, x64 or "Any CPU"? The versions of PI AF SDK and PI SDK are useful as well.
I'm using ASP.NET MVC 5. It targets Any CPU. The AF SDK was installed with PI AF Client_2014 R2 and has a file version of 188.8.131.5238. The PI SDK is version 184.108.40.2064.
See this thread for a discussion for this issue and some solutions: vcampus.osisoft.com/.../5133.aspx
Here are two solutions from that thread:
You should continue to build as AnyCPU. There are two workarounds:
1. In your post-build event command line settings for your project, delete the PI SDK assemblies which the build is copying into your bin directory
2. Add the 3 assemblies above from Program Files\PIPC\PISDK\PublicAssemblies to you project, and make sure the Copy Local setting is set to false.
Both solutions are a little weird, but either should work.
You're my hero David! That was the exact problem and the workaround did work for me! Back I go to work!! =)