Updating existing entities in Entity Framework 6 code-first

Question

I have an issue updating an existing entity in Entity Framework 6.

My generic update method is as follows:

public virtual void Update(T entity)
{
    if (entity == null) 
       throw new ArgumentNullException("entity");

    _context.Entry(entity).State = System.Data.Entity.EntityState.Modified;
    _context.SaveChanges();
}

where the constructor is:

protected IContext _context;
protected IDbSet<T> _dbset;

public EntityService(IContext context)
{
    _context = context;
    _dbset = _context.Set<T>();
}

IContext is basically an interface of DbContext.

Now when trying to update I get the following error;

InnerException = {"The UPDATE statement conflicted with the FOREIGN KEY constraint \"FK_dbo.Appointment_dbo.Driver_DriverID\". The conflict occurred in database \"DEVDB\", table \"dbo.Driver\", column 'id'.\r\nThe statement has been terminated."}

Now the classes (reduced for brevity) are:

public partial class Appointment : AuditableEntity<int>
{
        public override int ID { get; set; }

        [ForeignKey("AppointmentType")]
        public int AppointmentTypeID { get; set; }
        public virtual AppointmentType AppointmentType { get; set; }

        [ForeignKey("AppointmentStatus")]
        public int AppointmentStatusID { get; set; }
        public virtual AppointmentStatus AppointmentStatus { get; set; }

        [ForeignKey("Driver")]
        public int? DriverID { get; set; }
        public virtual Driver Driver { get; set; }

        [ForeignKey("Vehicle")]
        public int? VehicleID { get; set; }
        public virtual Vehicle Vehicle { get; set; }
    }

Now I have tried passing the result in through both entities.

i.e. VehicleID = 1 with Vehicle = null, VehicleID = null with Vehicle = VehicleEntity, and also together.

See the screenshot of the entity contents example:

Any ideas why this is occurring please?

Answer 1

It's occuring because DriverID is 0, but there is no Driver in the DB with an ID of 0. Since DriverID is nullable, you can probably get away with a DriverID of null

I can't elaborate much more on that unless I see what happens before you call the Update method.