Today I finished developing a plugin. As the new plugin was part of a project containing more plugins, I updated the version number in the AssemblyInfo.cs from 126.96.36.199 to 188.8.131.52. I compiled the solution, ran ILMerge and fired up the plugin registration tool.
I connected to my environment, picked the existing plugin assmbly and performed the upgrade and registered the new plugin steps.
Then I noticed something funky… The plugin assembly showed up twice in the list. Weird! Within minutes I had some complaining testers on the phone
It turns out that CRM is a bit picky on version numbers. If you update either the major or minor version of a plugin assembly, a new registration is made instead of performing an upgrade. After pulling the new assembly and changing the version number to 184.108.40.206 the upgrade went butter smooth.
Note to self: when doing upgrades to the Plugin assembly, just increment the revision number in the AssemblyInfo.cs.