Question

I have a scenario I’m getting a little muddled with using EF code first. The classes I’ve created are below:

public class Company
{
    public int Id { get; set; }
    public List<Contact> Contacts { get; set; }
    public List<Job> Jobs { get; set; }
}

public class Contact
{
    public int Id { get; set; }
    [ForeignKey("CompanyId")]
    public virtual Company Company { get; set; }
    public int CompanyId { get; set; }       
    public List<Job> Jobs { get; set; }
}

public class Job
{
    public int Id { get; set; }
    [ForeignKey("CompanyContactId")]
    public virtual CompanyContact CompanyContact { get; set; }
    public int CompanyContactId { get; set; }
    [ForeignKey("CompanyId")]
    public virtual Company Company { get; set; }
    public int CompanyId { get; set; } 
}    

However, when I build the DB I get the following error:

Introducing FOREIGN KEY constraint ‘FK_Contacts_Company_CompanyId’ on table ‘Contacts’ may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

So a little research indicates the answer to this is to use the Fluent API to define the mappings as required but I can’t get my head around how to do this or find an example of a similar scenario.

I realise I could remove the Company class from Job and navigate through Contact but I’d prefer not to if possible.

Any help gratefully received

Answer 1

You want to use the EF model builder to set up these relationships.

An example of how you would do this for one of your properties would be the following:

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Contact>().HasOptional(e => e.Company).WithMany(c=>c.Contacts);
    } 

For more of an explanation around how to use the modelbuilder take a look at my article on EF Navigation Properties