EF does not currently support relationships defined in terms of non-primary key unique constraints. The work item tracking this is https://entityframework.codeplex.com/workitem/299 You may want to vote for this item and/or the feature request on user voice: http://data.uservoice.com/forums/72025-entity-framework-feature-suggestions/suggestions/1050579-unique-constraint-i-e-candidate-key-support
Support for unique constraints is relatively high on our backlog of features to implement in EF, although it unfortunately won't be included in the EF6 release.
Support for unique constraints is relatively high on our backlog of features to implement in EF, although it unfortunately won't be included in the EF6 release.