MS CRM 4 - Custom entity with "regardingobjectid" functionality

Question

I've made a custom entity that will work as an data modification audit (any entity modified will trigger creating an instance of this entity). So far I have the plugin working fine (tracking old and new versions of properties changed).

I'd like to also keep track of what entity this is related to. At first I added a N:1 from DataHistory to Task (eg.) and I can indeed link back to the original task (via a "new_tasksid" attribute I added to DataHistory).

The problem is every entity I want to log will need a separate attribute id (and an additional entry in the form!)

Looking at how phone, task, etc utilize a "regardingobjectid", this is what I should do. Unfortunately, when I try to add a "dataobjectid" and map it to eg Task and PhoneCall, it complains (on the second save), that the reference needs to be unique. How does the CRM get around this and can I emulate it?

Answer 1

CRM has a special lookup type that can lookup to many entity types. That functionality isn't available to us customizers, unfortunately. Your best bet is to add each relationship that could be regarding and hide the lookups that aren't in use for this particular entity.

Answer 2

You could create your generic "dataobjectid" field, but make it a text field and store the guid of the object there. You would lose the native grids for looking at the audit records, and you wouldn't be able to join these entities through advanced find, fetch or query expressions, but if that's not important, then you can whip up an ASPX page that displays the audit logs for that record in whatever format you choose and avoid making new relationships for every entity you want to audit.