Validation failed for one or more entities. See 'EntityValidationErrors' property for more details [duplicate]

Answer 1

I had to write this in the Immediate window :3

(((exception as System.Data.Entity.Validation.DbEntityValidationException).EntityValidationErrors as System.Collections.Generic.List)[0].ValidationErrors as System.Collections.Generic.List)[0]

in order to get deep into the exact error !