We have custom attribute edit screens written in VB6 for ArcMap 9.2 that use GDB_OBJECTCLASSES.EXTCLSID. When we copy the layer to ArcGIS 10 the custom screens come up nicely but of course don't work so I have a few questions.
Where is the EXTCLSID now stored in the new ArcGIS 10 geodatabase tables so I can remove the reference to old screens?
I know that in ArcGIS 10 the custom attribute edit screens will need to be re-written in .net but do they come in as COM component still or are they now supposed to be add-ins?
In short, Add-Ins aren't the answer in this case; the attribute editor is still referenced via COM, although it has .NET bindings that are used instead. An EXTCLSID is still required, but its mechanics may be different from your pre-existing solution. I'd have a look at the above referenced sample to see if your solution can be migrated, or if you're better of writing a new one from scratch.