EF Code First One To Many. Cannot Seed

Question

I am trying to seed a code first database; in particular a one to many relationship. Whatever combinations of annotations and properties I use I cannot get it to work.

One Course can have many Applicants. I want EF to insert the ApplicantId (identity). I will set CourseId

Models

    //One
    public class Course
    {
        public Course()
        {
            Applicants = new List<Applicant>();
        }
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public string CourseId { get; set; }

        public virtual ICollection<Applicant> Applicants { get; set; }
   }

    //Many
    public class Applicant
    {
        public int ApplicantId { get; set; }

        public string CourseId { get; set; }

        [ForeignKey("CourseId")]
        public virtual Course Course { get; set; } 
    }

Seed

    var course = new Data.Models.Course
    {
          CourseId = "myId",
          Email = "[email protected]"
    };

    var applicant =
                new Applicant
               {
                   CourseId = "myId",
                   Forename = "Ryan",
                   Surname = "Giggs"
               };

   course.Applicants.Add(applicant);
   context.Courses.AddOrUpdate(course);

The Id field is required

The models and seed above give me an "Id Field is required" error. I assumed this was because I was not setting the ApplicantId - even though I expected EF to do this for me by convention.

So I tried explicitly setting the ApplicantId...

   var applicant =
                    new Applicant
                   { 
                       ApplicantId = 1,
                       CourseId = "myId",
                       Forename = "Ryan",
                       Surname = "Giggs"
                   };

but got the same error.

Cannot insert the value NULL into column

I then tried explicitly informing EF that ApplicantID is an identity column.

    public class Applicant
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int ApplicantId { get; set; }

        //rest as before
    }

But now I get this error:

'ApplicantId', table 'Context1.dbo.Applicant'; column does not allow nulls. INSERT fails.

Note I do not have any code in my modelbuilder since it is my understanding this is only required if model definitions do not follow convention.

EDIT I have created a quick console app which includes just the two models above and the seed method. It works without an issue. I'll therefore try spot a difference between this and the main solution.

Answer 1

I have not been able to determine why the validation was failing on seed. As mentioned in the update to the question, I was able to get exactly the same relationship working in a quick console app.

Luckily at present, existing data and prior migrations are not important and thus I was able to delete all migrations and create the database from scratch.

This time around the seed method raised no validation errors and populated the data as expected.

The answer here was useful: How to re-create database for Entity Framework?

In fact, since posting this question, I've had to to this a couple of times. Somehow some of the migrations I am performing are leaving the database in a state which prevents further updates from succeeding.