Why do I get this .NET error - “TypeError: expected List[DataPoint], got List[DataPoint]”

Question

I refactored some code, and now I get this error when calling a function. But everything seems to be fine, I even compared failing_argument.GetType().AssemblyQualified

Answer 1

After further debugging I managed to get a different error message from the code: Unable to cast object of type 'List[DataPoint]' to 'List[DataPoint]'

Searching for this yielded a couple of articles explaining the problem:
http://www.infinitec.de/post/2008/05/InvalidCastException-Unable-to-cast-object-of-Type-X-to-X.aspx
http://geekswithblogs.net/rupreet/archive/2010/02/16/137988.aspx

It turns out that the assembly containing DataPoint (from List[DataPoint]) it's loaded twice in my application from two different locations. The cause in my case is that when Visual Studio builds an assembly, it also copies all the other referenced assemblies next to the newly built one in the bin folder. But I also dynamically load one of the referenced assemblies from it's original build location.