Entity Framework Core - 关系

Question

I have 2 classes and I am looking for the best way to configure a relationship between them.

  public class Ride
    {
        public int Id { get; set; }
        public virtual Address StartPoint { get; set; }
        public virtual Address EndPoint { get; set; }
    }

    public class Address
    {
        public string Id { get; set; }
        public string Name { get; set; }
        public decimal LocationLat { get; set; }
        public decimal LocationLng { get; set; }

    }

At the moment when I create a new ride, a new address is created automatically.

How can I check if the address already exists in the database (by id), and if it does - navigate towards that address (not create a new one).

Answer 1

I assume that your problem relates to incorrect entry state of address entities. You can use method TrackGraph to traverse all objects relates to newRide entity and change entry state to Unchanged if id exists:

var newRide = new Ride();
newRide.StartPoint = new Address{...} //set Id property

context.Rides.Add(newRide);
context.ChangeTracker.TrackGraph(newRide, e => {
                                                if (e.Entry.IsKeySet)
                                                {
                                                    e.Entry.State = EntityState.Unchanged;
                                                }
                                                else
                                                {
                                                    e.Entry.State = EntityState.Added;
                                                }
                                            });
context.SaveChanges();