Doesn't even need to be an abstract base class. It's just as easy to use reflection to find all implementations in an assembly of an IMigration interface.

(ETA: Though my favorite pattern here became using DI for this instead of reflection. For every IMigration have a `services.AddTransient<IMigration, SomeMigrationImplementationClass>()` somewhere and then your service to run all migrations can just request from DI `IEnumerable<IMigration>`. I can then put the Reflection into a unit test to make sure everything that implements IMigration is registered in the DI container. But using DI in the main assembly to register all the migrations rather than Reflection leaves more room to try to AOT compile the assembly in production builds.)

Assuming you have all the code in your solution, you could do this with a source generator instead and have no need of reflection and are AOT compatible

yeah, there's plenty of ways to do that. I like having the attribute there so that there is a strong hint that some magic is happening somewhere with that class.