SharePoint 2010 introduces some new features in the lookup fields area.
The bad news are, I'm afraid, that still all lookups are restricted to the same site collection.
But, from now on you will be able to include more then one field in the remote list when creating a lookup. So that if you are creating a lookup to "customers" list, you can ask to see customer's first name, last name, company and email instead of just "full name" or "customer name" as before.
Another new feature allows you to enforce your lookup data integrity, meaning you can either prevent deleting an item that has other items connected to it, or cascade the delete action to delete all dependant items.
This is good for customers who has "project" list and "project tasks" list, where a task is connected to a project.
So, by deleting a project you can make sure that all that project tasks are also deleted.
Or - if you'd like, to prevent deleting a project wiht active tasks! which is also cool.
Finally, there are some news on reverse lookup. Although SharePoint 2010 does not fully support reverse lookup fields it has a new API for getting all related items for a specific list items.
This means, that this new API will get all items in SharePoint that has a lookup that is connected to the current item. This new API also comes with a new web part OOTB you can just drop at any list item view form to see its connected items.
But still, if you want real reverse lookup functionality you will have to go with a 3rd party solution like KWizCom's Cascading lookup plus field type currently available for SharePoint 2007 but will be upgraded as soon as there is a public release of 2010.
Another thing that is greatly missing (and is available in our cascading lookup) is... Cascading feature! :) I mean the option to filter items in one lookup field based on one or more other fields on the same page. Thus creating a 2 or more levels of dependant fields (Country/City/Street fields for example)
Well, good thing SharePoint 2010 is not perfect - gives us more work to do, right? :)
Enjoy your migraion!
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