from http://community.devexpress.com//forums/p/63143/214423.aspx#214423
I linked the Mechanic Role, then saved. Then clicked on Link again - Lookup still shows the Mechanic Role.
A Role which has already been linked must be filtered out from the Lookup when it only can be linked once.
We have closed this ticket because another page addresses its subject:
SystemModules.Link - Exclude objects that are already linked to an object from the Link ListView