CODEWITHSUNDEEP
entity-frameworkmappingentity-framework-4.1ef-code-first
Guillermo Oramas R.
Guillermo Oramas R.

Reputation: 1303

Help with EF Code First, many to many relationship

Person and EHR(electronic health record) are one to one related. Person has EHRId nullable and EHR has PersonId not nullable.

At the same time EHR and Person must be many to many related. Because a person can have many medics (represented by person entity) and a medic can have many EHRs. I would like to have extra attributes on the join table.

I dont know how to define this in EF.

Please help.

Here are my classes.

    public class Person
        {
            public int ID { get; set; }            
            public string firstName { get; set; }            
            public string lastName { get; set; }            
            public ICollection<UserSpecialist> patients { get; set; }
            public int ehrID { get; set; }
            public virtual EHR ehr { get; set; }

        }

public class EHR
    {
        public int ID { get; set; }
        public bool asthmatic{ get; set; }
        public ICollection<UserSpecialist> specialists { get; set; }
        public int PersonID { get; set; }
        public virtual Person Person { get; set; }
    }

public class UserSpecialist
    {
        public int ID { get; set; }
        public DateTime creationDate { get; set; }
        public int PersonID { get; set; }
        public int EHRID { get; set; }
        public virtual Person Person { get; set; }
        public virtual EHR EHR { get; set; }
    }

When EF tries to create the database throws this error

Unable to determine the principal end of an association between the types 'Project.Person' and 'Project.EHR'. The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations.

Please help

Upvotes: 1

Views: 681

Answers (1)

Ladislav Mrnka
Ladislav Mrnka

Reputation: 364269

Person and EHR are not one-to-one related and they cannot be in EF. What you have defined is bidirectional one-to-many. You have also declared both relations as required because FK's are not nullable.

Real one-to-one can be defined in EF only if EHR's PK (Id) is also FK to Person. Once you define this the part with many-to-many becomes really strange because Person will be related with EHRs of other persons. You domain description is most probably not correct.

Upvotes: 2

Related Questions