Every one of us, software developers, experienced situations where the .Net Framework could not locate an assembly and ended up facing the TypeLoadException. These failures usually happen due to an assembly deployed to the wrong location or a mismatch in version numbers or cultures. A quick way to check what went wrong is to open the module window (Visual Studio) during debugging but that may be sometimes impossible or inconvenient because:

• We may not have Visual Studio installed. 
• We installed the product in the customer site and we don’t have the code available.
• It is some third party assemblies which causes the problems.

Luckily, there is an assembly binding log viewer which displays information that helps us diagnose why the .NET Framework can not locate an assembly at run time. This tool is called

I am currently working on a project with a pluggable application (load plugins at runtime and execute them) that loads assemblies at runtime, using the Assembly.LoadFile() method. I wanted to test it using NUnit (feel free to read our 3 Ways to Run NUnit from Visual Studio post). Although, the code was functioning very well it always failed during the NUnit tests, always! It took me several days to understand what went wrong and I want to share you with my findings.