PerformUpgrade Failed - In What Manner?

I'm in the midst both of developing and using a custom Transformation. Of course, every time I change the assembly version and reopen Visual Studio, I get the error:


DTS.Pipeline: The component metadata for "component "Map SERVICE_CERT String Locale" (195692)" could not be upgraded to the newer version of the component. The PerformUpgrade method failed.

Out of curiosity, I'm wondering, how did it fail? Did it throw an exception? Was it even called? Is it my PerformUpgrade override that is being referred to, or perhaps the base class version?

I've seen several of the threads on this topic in this forum, but they haven't completely solved the problem (I will take the step of creating a policy assembly later today, and maybe that's the problem).

But, is there a reference somewhere to exactly what's going on at package load time as far as loading custom components? I'd love to know which methods are called, in which order, and how SSIS decides which version of the component to load.

I'd also love to see some best practices for component development. For instance, maybe I shouldn't allow the assembly version to change during development? Do I need to remove and re-add the component from the toolbox, and does that affect components already in the package?

Sorry to ask questions I'd no doubt answer for myself within a few months, but this project is due at the end of this month!