Get entity member from key in Entity Framework

Question

In a project that involves an Asp.Net Core API and Entity Framework, I have the following entities:

public class A
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public string Id { get; private set; }

    [Required] public string Name { get; set; }

    [Required] public B MyObj { get; set; }
}

public class B
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public string Id { get; private set; }
}

My API has this model, which represents a POST request body for the creation of a new A:

public class A_Post
{
    public string Name { get; set; }

    public string Obj_Id { get; set; }
}

Here, Obj_Id refers to the Id of the B instance that I want A.MyObj to have as its value.

What I want to do is add a method to A that creates an instance of A from an instance of A_Post. Something like this:

public static A CreateFromPost(A_Post post)
{
    var entity = new A();
    entity.Name = post.Name;
    // post.Obj_Id is accessible here, but cannot set entity.MyObj
    return entity;
}

However, I'm not sure how to go from having the Obj_Id to having the entity it corresponds to, without getting it from the context. Is there a way to do this? Or will I have to set MyObj somewhere else in the program, where the context can be accessed?

The most obvious thing to do: add the primitive foreign key property to `A`. — Gert Arnold, Oct 14 '17 at 12:41
@GertArnold Can you please elaborate on that? What exactly needs to be added, and what would the result be? — stelioslogothetis, Oct 14 '17 at 12:43
you can also try attaching your `entity.MyObj` when you save your `entity`: https://stackoverflow.com/questions/46745226/unable-to-resolve-service-for-type?noredirect=1#comment80436678_46745226 — Khanh TO, Oct 14 '17 at 14:00

Get entity member from key in Entity Framework

0 Answers0