Entity Framework relations questions

Question

I have three classes

public class SPR
{
    public int ID { get; set; }     
    public string SubmittedBy { get; set; }
    public virtual ICollection<SPRItem> AllItems { get; set; }


}
public class SPRItem
{
    [Key]
    public int ID { get; set; }

    public string manufacturer { get; set; }   

    [ForeignKey("SPRItemDetails")]
    public virtual SPRItemDetails ItemDetails { get; set; }      

    public string requestedMinimumQuantity { get; set; }

    public virtual SPR SPR { get; set; }

}


public class SPRItemDetails
    {
        public int ID { get; set; }

        public string ItemNumber { get; set; } 

        public virtual SPRItem SPRItem { get; set; }  


    }

So the SPR class has a collection of SPRItem and which has the ItemDetails object.

I have a web API method which maps the data to the SPR object and fills in the SPRItem list and ItemDetails object. But whenever I am trying to save it using Entity Framework code first I am getting this error

{"Message":"An error has occurred.","ExceptionMessage":"Unable to determine the principal end of an association between the types 'SharePoint.MultiSPR.Service.Models.SPRItemDetails' and 'SharePoint.MultiSPR.Service.Models.SPRItem'. The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations.

This is my Context

public System.Data.Entity.DbSet<SharePoint.MultiSPR.Service.Models.SPR> SPRs { get; set; }

    public System.Data.Entity.DbSet<SharePoint.MultiSPR.Service.Models.SPRItem> SPRItem { get; set; }

    public System.Data.Entity.DbSet<SharePoint.MultiSPR.Service.Models.SPRItemDetails> SPRItemDetails { get; set; }

Can someone please tell me how to configure the relations correctly.

Thanks

score 0 · Answer 1 · answered Jun 09 '16 at 20:42

In a 1:1 relation you always have to indicate the principal and the dependent entity. The principal entity is the one that is most independent of the other, in this case SPRItem, presumably.

Next thing to decide is whether the relationship should be optional or required. I think, judging by the entity names, an SPRItemDetails will never exist without an SPRItem, so the relationship is 1:0..1 (not 0..1:0..1). Here's how to configure that:

modelBuilder.Entity<SPRItem>()
            .HasOptional(si => si.ItemDetails)
            .WithRequired(id => id.SPRItem);

This creates (or requires) an SPRItemDetails table having a primary key that's also a foreign key to SPRItem.

Entity Framework relations questions

1 Answers1