实现实体框架一对一关系

Question

I am trying to realize a one-to-one relation in Entity Framework with Code First. I want to create an Airplane table which has a FlightPlan.

Airplane:

public class Airplane
{
    [Key]
    public int AirplaneId { get; set; }
    public int Capacity { get; set; }
    public AirplaneStatus AirplaneStatus { get; set; }
    public int AmountOfPassengers { get; set; }
    public int AirfieldId { get; set; }

    public virtual FlightPlan FlightPlan { get; set; }
}

FlightPlan:

public class FlightPlan
{
    [Key]
    [ForeignKey("Airplane")]
    public int AirplaneId { get; set; }
    public int AirfieldFrom { get; set; }
    public int AirfieldTo { get; set; }
    public int AmountOfPassengers { get; set; }

    public virtual Airplane Airplane { get; set; }
}

When i initialize these classes with Migrations the following table structure is created:

After i manage to create an Airplane with a FlightPlan, which takes some workarounds, the Airplane doesn't have a Flightplan no matter what i try.

How can i solve this?

Edit

For testing purposes i add a FlightPlan to every updated Airplane. After fixing this a route is created for adding a Flightplan. The code is:

var airplane = _context.Airplanes.Find(model.AirplaneId);
var flightplan = new FlightPlan() { AirfieldFrom = 1, AirfieldTo = 2, AmountOfPassengers = 30 };
airplane.FlightPlan = flightplan;
_context.SaveChanges();

The solution for my problem is to force EF to include the FlightPlan when retrieving an Airplane.

Answer 1

This is most likely due to lazy loading since your FlightPlan is virtual .

var airplane = db.Airplanes.First(); //pull airplane from db
var passengerAmount = airplane.FlightPlan.AmountOfPassengers //attempting to use 
// FlightPlan property after pulling Airplane from db should load the FlightPlan

You can also force EF to include the FlightPlan property when pulling from the db.

using System.Data.Entity;
var airplane = db.Airplanes.Include(m => m.FlightPlan).First();

Answer 2

Should be done in the following way:

public class Airplane
{
    [Key]
    public int Id { get; private set; }

    public virtual FlightPlan FlightPlan { get; private set; }

    // ... other properties
}

public class FlightPlan
{
    [Key]
    public int Id { get; private set; }

    public virtual Airplane Airplane { get; private set; }

    // ... other properties
}

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
     modelBuilder.Entity<FlightPlan>()
       .HasRequired(flightPlan => flightPlan.Airplane)
       .WithOptional(airplane => airplane.FlightPlan);

       base.OnModelCreating(modelBuilder);
}

Your setters of course could be public .