Complex type collection support

[AndriySvyryd]

The collections need to be ordered, since they will be mapped to JSON arrays. (Unless we allow to map to objects, see #28861)

This only covers collections of reference types. For value types see #31411

• Model building and validation
• Compiled model support
• Refactor change tracking property accessors
• Change tracking support
• Update pipeline support
• Convention to automatically configure nested properties inside complex types as complex properties (and not navigations)
• Query support (#36296, @roji)
• ExecuteUpdate support

[roji]

Note also #11799 which is about supporting tuples as well.

[rlcarrierscsharp]

I don't suppose I could get lucky enough to have someone from the EF Core team at a high level explain what changes would need to be made to get this to work? I really have a need for this now and it would be great to make the changes on my own while I wait for this to be officially completed. Or at least get the change tracking working, even if the database doesn't actually get updated would be fine.

I can see that the ComplexProperty already has the IsCollection property on it. Would changes just need to be made to the SnapshotFactoryFactory, ValueComparer, and NavigationFixer classes - again, without concern of generating the proper database statements to sync the data model with the database - in order to have complex collections have change tracking support?

[roji]

This is a pretty deep change requiring adjustments in many different components of EF (modeling, change tracking, querying, updating...), it's unlikely you'll be able to correctly and easily do these changes on your own as a quick project etc.

Remember that you can currently already use owned entities as collections in order to map JSON. This is the recommend thing until complex type collection support is built into EF.