Entity Framework Foreign Key as Primary Key Code First

c#, ef-code-first, entity-framework

Solution

I thought I'd give this a shot and it worked nicely.

public class FooState
{
    [Required]
    [Key]
    [ForeignKey("Foo")]
    public int FooStateId { get; set; }

    [Required]
    public int State { get; set; }

    public Foo Foo { get; set; }
}

Problem

I have two code first models, Foo and FooState where Foo has an optional FooState. ``` public class Foo { [Key] public int FooId { get; set; } public FooState FooState { get; set; } } public class FooState { [Key] public int FooStateId { get; set; } [Required] public int State { get; set; } [Required] public Foo Foo { get; set; } } ``` This works fine however when I try to add the foreign key to FooState like so ``` public class FooState { [Key] public int FooStateId { get; set; } [Required] public int State { get; set; } [ForeignKey("Foo")] [Required] public int FooId public Foo Foo { get; set; } } ``` It all falls over because FooStateId is really using FooId as it's primary key. This makes sense from a database point of view. I would however like not to have to populate an instance of Foo when saving the FooState record but still retain the required attribute. This would allow me to send down a FooId and state in a dto and not have to retrieve the whole Foo object from the DB if I want to make a change to its state. How should I be setting this up with EF code first?

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