How to map two properties in one code first object to the same parent type

Question

I've been at this for hours and have tried many suggestions I found searching but no luck. I'm using code first EF 5.

The situation is that I have a class Employee. Then I have another class that has two properties on it, both are of type Employee. I want these both to be foreign key constraints but the requirements allow many of the same requests to and from the same users so I can't just use them as keys. I don't really care about Employee having the two collections for navigation but in my working through the problem that seemed a requirement. If it simplifies the problem I can remove those.

I get this message. System.Data.Entity.Edm.EdmAssociationEnd: : Multiplicity is not valid in Role 'Employee_RequestsForEmployee_Target' in relationship 'Employee_RequestsForEmployee'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be '*'.

I've tried this using the Fluent API in the OnModelCreation method of the context;

modelBuilder.Entity() .HasRequired(u => u.ForEmployee) .WithMany() .HasForeignKey(u => u.ForEmployeeId);
        modelBuilder.Entity<RevenueTransferRequest>()
                    .HasRequired(u => u.FromEmployee)
                    .WithMany()
                    .HasForeignKey(u => u.FromEmployeeId);

The classes in conflict are (I've removed some properties for clarity);

    public class Employee : IEmployee
    {
        [Key]
        public string Id { get; set; }

        [InverseProperty("ForEmployee")]
        public ICollection<RevenueTransferRequest> RequestsForEmployee { get; set; }

        [InverseProperty("FromEmployee")]
        public ICollection<RevenueTransferRequest> RequestsFromEmployee { get; set; }
    }

 public class RevenueTransferRequest : IRevenueTransferRequest
    {
        [Key]
        public Guid Id { get; set; }

        [Required]
        [ForeignKey("ForEmployee")]
        public String ForEmployeeId { get; set; }

        [InverseProperty("RequestsForEmployee")]
        public Employee ForEmployee { get; set; }

        [Required]
        [ForeignKey("FromEmployee")]
        public String FromEmployeeId { get; set; }

        [InverseProperty("RequestsFromEmployee")]
        public Employee FromEmployee { get; set; }
    }

Any help would be much appreciated. Thanks in advance.

Interesting question. Would deriving a RevenueTransferRequestFromEmployee from Employee be overkill? Thinking out loud here... just to point out, the [Key] attribute is not needed if it's sitting on top of a property that's named [typename]Id or Id, because Entity Framework finds the key by convention over configuration. — Mathieu Guindon
In the end I removed all the InverseProperty and ForiegnKey definitions and took the collections off of the Employee table. it works and the keys are there. This gets me moving forward on this project. I'm going to continue researching this in my spare time and I'll return with a solution when I find it. — Honorable Chow

Honorable Chow Honorable Chow · Accepted Answer · 2013-02-15T21:36:14

I never did figure out how to do it using data annotations but using the Fluent API I was able to do it. What I was missing was that I had to specify in the HasMany() method what the relationship on the other side was which I assumed was understood through the data annotations and conventions.

This is called in the DbContext OnModelCreating override (The WillCascadeOnDelete(false) is related to another issue).

    modelBuilder.Entity<RevenueTransferRequest>()
                .HasRequired(e => e.FromEmployee)
                .WithMany(x=>x.RequestsFromEmployee)
                .WillCascadeOnDelete(false);

    modelBuilder.Entity<RevenueTransferRequest>()
              .HasRequired(e => e.ForEmployee)
              .WithMany(x => x.RequestsForEmployee)
              .WillCascadeOnDelete(false);

With the classes:

[Key]
        public String Id { get; set; }

        public String BusinessUnitLeaderId { get; set; }

        public Employee BusinessUnitLeader { get; set; }

        [Required]
        [MaxLength(150)]
        public String DisplayName { get; set; }

        public ICollection<Project> BusinessUnitLeaderProjects { get; set; }

        public ICollection<RevenueTransferRequest> RequestsForEmployee { get; set; }

        public ICollection<RevenueTransferRequest> RequestsFromEmployee { get; set; } 

public class RevenueTransferRequest
    {
        [Key]
        public Guid Id { get; set; }

        [Required]
        public String ForEmployeeId { get; set; }

        public Employee ForEmployee { get; set; }

        [Required]
        public String FromEmployeeId { get; set; }

        public Employee FromEmployee { get; set; }

        [Required]
        public String ProjectId { get; set; }

        public Project Project { get; set; }

        [Required]
        public Double? TransferAmount { get; set; }

        public int WorkflowState { get; set; }
    }

How to map two properties in one code first object to the same parent type

1 Answers