MissingMethodException when calling to a class library from third-party application

Question

I'm getting a MissingMethodException (referencing a specific method) when calling a method in a company library from a third-party application with scripting, OnBase. The object the method is called on already exists and succeeds other calls before this point.

Things I've confirmed:

• Other references from this library work correctly
• Method is public
• Version of DLL referenced by the script in question has the method (rebuilt the assembly and re-imported it, outputs show current date as created date, and OnBase shows the correct updated version number)
• No versions of the DLL are in the GAC
• Server application has been restarted since importing

Also of note is that the script editor's code completion in OnBase can't find the method either, but it also succeeds building.

• What are the more uncommon locations where I should be looking for an old DLL?
• Are there any OnBase specific locations?
• What other causes can there be?

Answer 1

To clarify, assembly 1 is referenced by the script and contains the method that's coming back missing, and assembly 2 is referenced by assembly 1 and the script both. Assembly 2 works in all cases, assembly 1 works except this one method.

The reason this was happening was that assembly 1 and the script were referencing different versions of assembly 2, so when we were trying to pass in an object defined in assembly 2 to the method in assembly 1, it was from a version that didn't match and so what was missing was a method with that specific signature, ie DoStuff(v1.Foo) existed but DoStuff(v2.Foo) didn't. Obviously, the error only stated that DoStuff(Foo) was missing.