CODEWITHSUNDEEP
c#entity-framework
Iztoksson
Iztoksson

Reputation: 990

Adding entity one-to-many where parent already exists

I have a simple model of Motorcycle and Person. Many people can rent one motorcycle, so it's a one-to-many relationship.

I have this set as a Repository with Unit of work (code below).

Now I have a motorcycle already in my database (MotorcycleId = 1), and I would like to insert a list of people that have rented this motorcycle. The problem is that every time I insert a list of Person a new motorcycle is also inserted.

How can I insert a Person with an existing motorcycle?

Models:

namespace CodeFirst.Model
{

    using System.Collections.Generic;

    public class Motorcycle
    {
        public int MotorcycleId { get; set; }
        public int ModelYear { get; set; }
        public int Displacement { get; set; }
        public decimal Killowatts { get; set; }
        public string ModelName { get; set; }
        public virtual ICollection<Person> Persons { get; set; }
    }
}

namespace CodeFirst.Model
{
    public class Person
    {
        public int PersonId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public virtual Motorcycle Motorcycle { get; set; }
    }
}

Repository method for adding list of entities:

public void Add(List<T> entityList)
{
    foreach (T item in entityList)
    {
        DbEntityEntry dbEntityEntry = _dbContext.Entry(item);
        if (dbEntityEntry.State != EntityState.Detached)
        {
            dbEntityEntry.State = EntityState.Added;
        }
        else
        {
            _dbSet.Add(item);
        }
    }
}

Test method, get motorcycle with id=1 and attach it to each person:

static void AddPersons()
{
    var unitOfWork = new UnitOfWork.UnitOfWork();
    var personList = new List<Model.Person>();
    var motorcycle = unitOfWork.Motorcycles.GetById(1);

    personList.Add(new Model.Person() { FirstName = "Jim", LastName = "Morrison", Motorcycle = motorcycle });
    personList.Add(new Model.Person() { FirstName = "Jimmy", LastName = "Hoffa", Motorcycle = motorcycle });
    personList.Add(new Model.Person() { FirstName = "Arlo", LastName = "Guthrie", Motorcycle = motorcycle });

    unitOfWork.Persons.Add(personList);

    unitOfWork.Commit();
}

Upvotes: 0

Views: 59

Answers (2)

Pedram
Pedram

Reputation: 828

Check the relationships between tables in your db and make sure that everything is ok,then change the code and try this:

namespace CodeFirst.Model
{

    using System.Collections.Generic;

    public class Motorcycle
    {
        public int MotorcycleId { get; set; }
        public int ModelYear { get; set; }
        public int Displacement { get; set; }
        public decimal Killowatts { get; set; }
        public string ModelName { get; set; }

        public virtual ICollection<Person> Persons { get; set; }
    }
}

namespace CodeFirst.Model
{
    public class Person
    {
        public int PersonId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }

        public virtual Motorcycle Motorcycle { get; set; }
        [ForeignKey("Motorcycle")]
        public int MotorcycleId { get; set; }
    }
}

and :

static void AddPersons()
{
    var unitOfWork = new UnitOfWork.UnitOfWork();
    var personList = new List<Model.Person>();
    //var motorcycle = unitOfWork.Motorcycles.GetById(1); //not required
    var motorcycleId = 1;

    personList.Add(new Model.Person() { FirstName = "Jim", LastName = "Morrison", MotorcycleId = motorcycleId });
    personList.Add(new Model.Person() { FirstName = "Jimmy", LastName = "Hoffa", MotorcycleId = motorcycleId });
    personList.Add(new Model.Person() { FirstName = "Arlo", LastName = "Guthrie", MotorcycleId = motorcycleId });

    unitOfWork.Persons.Add(personList);

    unitOfWork.Commit();
}

Upvotes: 1

mrsargent
mrsargent

Reputation: 2442

try this

static void AddPersons()
{
var unitOfWork = new UnitOfWork.UnitOfWork();    
var motorcycle = unitOfWork.Motorcycles.GetById(1);
motorcycle.Persons.Add(new Person{FirstName = "Jim", LastName = "Morrison"});
unitOfWork.Commit()   
}

Upvotes: 1

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