Entity Framework Code First - Reference same table

Question

I am still starting with Entity Framework Code First. I want to be able to select a Resource from list when creating a new resource. How do I reference a Resource with a Resource model.

public class Resource
{

    public int ResourceId { get; set; }
    [Required]
    [DataType(DataType.EmailAddress)]
    [EmailAddress]
    public string EmailAddress { get; set; }
    [Required]
    public string Password { get; set; }
    public string FullName { get; set; }


    public int TimeManagerId { get; set; }

    public int TravelManagerId { get; set; }

    public int OvertimeManagerId { get; set; }

    public int AbsenceManagerId { get; set; }
    public virtual Resource TimeManager { get; set; }
    public virtual Resource TravelManager { get; set; }
    public virtual Resource OvertimeManager { get; set; }
    public virtual Resource AbsenceManager { get; set; }

}

This looks good. What's wrong with this? Do you get an error? What exactly is your question? — Kevin Brechbühl
– Kevin Brechbühl, Commented Feb 18, 2014 at 6:58
When I generate the controller, shouldn't the fields be dropdownlists? I currently just display int textfields — razeth01
– razeth01, Commented Feb 18, 2014 at 7:00
I don't understand what is logical model of this. But did you try anything? — Kirill Bestemyanov
– Kirill Bestemyanov, Commented Feb 18, 2014 at 7:00
@razeth01 this depends on your requirements. You current model says that every Resource has a TimeManager, a TravelManager etc. If you need to have a list of other resources, then you need to add a collection of resources: public virtual ICollection<Resource> MyResources { get; set; } — Kevin Brechbühl
– Kevin Brechbühl, Commented Feb 18, 2014 at 7:03

Anthony Chu · Accepted Answer · 2014-02-18 07:25:44Z

2

I think you're pretty close! If you want to do this by convention, you can change the foreign keys in your model to the form of [navigation property name][principal primary key property name]. Specifically, change Id to ResourceId so it matches the primary of the table you're referencing (which happens to be itself)...

public int TimeManagerResourceId { get; set; }
public int TravelManagerResourceId { get; set; }
public int OvertimeManagerResourceId { get; set; }
public int AbsenceManagerResourceId { get; set; }

Since you're just starting with EF code first, I'd recommend you install the Entity Framework Power Tools. You'll be able to right-click on the .cs file containing your DbContext, and it'll generate a read-only diagram of the mappings.

Try it out with your current model... right-click on entity in the diagram and view Table Mappings. You'll see EF wasn't able to figure out your foreign keys and created 4 more for you. Once you make the changes above, generate the diagram again and see the difference.

Edit: Docs on code first conventions... http://msdn.microsoft.com/en-us/data/jj679962.aspx

edited Feb 18, 2014 at 7:25

answered Feb 18, 2014 at 7:01

Anthony Chu

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1 Comment

Anthony Chu Over a year ago

Awesome! Just updated the post with a reference for code first conventions if you are interested. Also, these are often referred to as "self-referencing" or "hierarchical" entities... that's handy if you need to search for more information.

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