实体框架代码第一个数据库用于一对一到多个关联

Question

I'm building a database with entityframework using code first. The aim is to syncronize a remote database with webservice call. I already have a structured entities builded for webservice call function.

How do i need to code the dB context for create the following association ?

the cart.cs gives cart_row through AssociationsCartAux, as follow

public class order
{
    [Key]
    public long? id { get; set; }
    public long? id_cart { get; set; } //which is a foreign key
    public string invoice_number { get; set; }
    ....
}

public class cart
{
    public long? id { get; set; }
    ...
    public AssociationsCartAux associations { get; set; }
}

public class AssociationsCartAux : PrestaShopEntity
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long? id_virtual { get; set; }
    public List<cart_row> cart_rows { get; set; }

    public AssociationsCartAux()
    {
        this.cart_rows = new List<cart_row>();
    }
}

public class cart_row
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long? id_cartRow_fictive { get; set; }
    public long? id_product { get; set; }
    public int quantity { get; set; }
    ....
}

I tried the following code in my dbcontext file

    public DbSet<cart> cart { get; set; }
    public DbSet<cart_row> cart_row { get; set; }
    public DbSet<order> order { get; set; }

 protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<AssociationsCartAux>()
        .HasMany(p => p.cart_rows)
        .WithMany().Map(c =>
        {
            c.ToTable("cart_assocation");
        });

When i run the code, it's building the following tables

dbo.carts

dbo.cart_row

dbo.AssociationsCartAuxes

• id_virtual

dbo.cart_assocation <=== ASSOCIATION BETWEEN CART AND CART_ROW

• AssociationsCartAux_id_virtual

• cart_row_id_cartRow_fictive

when i reload the data syncronisation ==> no problem when i reload the data syncronisation with an order update ==> the dbo.AssociationsCartAuxes double in volume additionnaly to the existing data, despite of update the current data and add only the new one. Involving the lost of the linq association between cart and cart_row. Which let me suppose that i don't have correctly build my dbcontext.

I'm not familiar with entity framework so i tried some way to do this with putting AssociationsCartAux.cs as a ComplexType but not work because of cart_row object inside.

Thanks you in advance for any help.

For additionnal information, i put the way how i put data into the tables

            foreach (cart panier in listcart)
            {
                var result = ctx.cart.SingleOrDefault(b => b.id == panier.id);
                if (result == null)
                {
                    ctx.cart.Add(panier);
                    ctx.SaveChanges();
                }
            }

          foreach (order commande in listorder)
            {
                var result = ctx.order.SingleOrDefault(b => b.id == commande.id);
                if (result == null)
                {
                    ctx.order.Add(commande);
                    ctx.SaveChanges();
                }
            }

Answer 1

You don't need an auxiliar table for a one-to-many relationship, it's enough with:

public class cart
{
    public long? id { get; set; }
    ...
    public List<cart_row> cart_rows { get; set; }
}

And the magic of EF will do the rest, although it's a good idea to explicitly define the relationship in the other end as well:

public class cart_row
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public long? id_cartRow_fictive { get; set; }
    public long? id_product { get; set; }
    public int quantity { get; set; }
    ....
    public long? id_cart {get; set;}
    public cart cart {get; set;}
}

And in the DbContext:

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<cart_row>()
            .HasOne(cr => cr.cart)
            .WithMany(c => c.cart_rows)
            .HasForeignKey(cr => cr.id_cart);
    }

But there are many other ways in which you can achieve this, for more information check: https://docs.microsoft.com/en-us/ef/core/modeling/relationships

Answer 2

I found an answer, may be it could help someone to make a such third level association. Simply add : modelBuilder.Entity().ToTable("carts");

to the db context as follow.

in the db context :

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<cart>()
            .HasRequired(s => s.associations)
            .WithRequiredPrincipal(ad => ad.cart);

        modelBuilder.Entity<cart_row>()
            .HasRequired(cr => cr.AssociationsCartAux)
            .WithMany(c => c.cart_rows)
            .HasForeignKey(cr => cr.id_AssocCartAux);

        modelBuilder.Entity<AssociationsCartAux>().ToTable("carts"); <== this solved my issue