How to create a computed attribute from the msDS-ExternalDirectoryObjectId attribute from my backend Active Directory?

QUESTION:

How can I create a computed attribute based on the Active Directory attribute msDS-ExternalDirectoryObjectId?

ANSWER:

1. From Main Control Panel -> Settings -> Server Frontend -> Attributes handling, remove “ms*" from the Attributes excluded from search results (support for Active Directory) to ensure the value is returned from the backend AD.
2. On the Main Control Panel -> Directory Namespace tab, select the proxy view to the Active Directory backend.
3. With the proxy view of Active Directory selected, click the Attributes tab on the right.
4. Add the “msDS-ExternalDirectoryObjectId” attribute to the list and enter a Virtual Name that is available in the User object class definition (in the RadiantOne LDAP Schema). An example is “uid”.
5. Select the Always Requested option and then Save.
6. On the Objects tab, add the user object class in the Primary Objects section. 
7. Click Save.
8. At the bottom of the Objects tab, click Edit next to Define Computed Attributes.
9. Use the “uid” attribute as part of the value to define your computed attribute.
10. Save the virtual view.