C# project references

The 'dynamic' in DLL as far as C# is concerned, when you've included a DLL reference in your solution, only extends up to the point at which you compile the solution.

So if you have a class library, and a unit test to which you've added a reference to the library, it's no good fiddling with the library in the IDE while running your unit test from a prompt. The unit test will, it seems, have linked into itself the class library DLL as it was when you compiled the unit test: more of a statically linked library in this case.