This is an area where it seems that Microsoft has really listened to the community and made some serious investments into making it a really robust part of SharePoint 2010.
The “thing” previously known as the BDC has now gotten a huge facelift as is now a first class citizen in the platform.
Since I have looked a little bit at the new Entity Framework I can´t begin to see some similarities in the designers and look of the VS support.
This piece of technology makes it possible for us as developers, and the power users, to connect SharePoint to external data outside of SharePoint and make it not only readable via SharePoint, but now also updatable.
Things that we previously has to use some really ugly xml for can now be modeled in visual studio through a wonderful set of new designers.
In SharePoint 2010 we have a concept known as the external content type. That makes it possible for us to map a central metadata set, which will be indexed and searchable, to data that lives outside if SharePoint (the common scenario might be data in a separate SQL server table/s). This content type is then mapped to a new thing known as the external list, which behaves and looks like a standard SharePoint list. So now, the user can work with that data as though it lives inside of SharePoint. The user won´t see the difference.
We have the option to use both no code (SPD) and code (VS).
No code might be used by a power user to map customers to Outlook contacts or use them in InfoPath or Word. This is xml based.
Code is used when we need more control over security and we need business logic in forms. Now it becomes reusable (can be used in no code solutions) and we can use any office application like excel. We will now have entities that we as developers can program against, which looks a lot like using Entity Framework or some other domain model tool.
A demo was shown where data (customers) from a REST service with data from SQL server and was represented in SharePoint as an external list with an external content type. CRUD was enabled from within SharePoint which made that data updatable.
Then it was mapped against office content types (contacts in Outlook) so a customer was now a contact in Outlook. Data that was naturally mappable in Outlook still showed up as a list of read-only properties.
You could now edit the customers (contacts) in Outlook and the changes where propagated through the BCS into SQL server and the changes showed up in the REST service as well as within SharePoint.
An add-in for excel was also shown that made the data appear as a list and of course also manageable through that interface.
This was then packaged as a click once application and included in the WSP package and included in the SharePoint artifact in Visual Studio.
Great work! I can already see a number of scenarios where this will come in handy.