Object Browser: why do I get "not a valid .net assembly"?

In the ScaleOut Object Browser, when I try to add my .net built assemblies, using the Load/Unload assemblies option under tools, for my .net built assemblies, I get the error "XXXX.dll is not a valid .net assembly".

These are .net assemblies built using C#. What needs to be done, in order to getthese loaded, so that I can review the data in the cache.

Thanks in advance.