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How to configure many to many relationship using entity framework fluent API

Asked 2012-01-19T13:58:04.947
25

I'm trying to set up a many to many relationship in EF code first but the default conventions is getting it wrong. The following classes describes the relationship:

class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
}

class Account
{        
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Product> Products { get; set; }
}

One Account can have many Products.

However the EF conventions will create the DB tables as:

Products Table
--------------
Id
Name
Account_Id  <- What is this?

Accounts Table
--------------
Id
Name

This doesn't look like a many-to-many table structure? How can i get configure the fluent API to reflect the relationship and create an intermediary table:

AccountProducts Table
---------------------
Account_Id
Product_Id
c# entity-framework-4.1 ef-code-first associations
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3 Answers

59
modelBuilder.Entity<Account>()
            .HasMany(a => a.Products)
            .WithMany()
            .Map(x =>
            {
                x.MapLeftKey("Account_Id");
                x.MapRightKey("Product_Id");
                x.ToTable("AccountProducts");
            });
answered 2012-01-19T14:09:26.927
7

What EF has suggested is a one-to-many relationship.

One Account can have many Products, i.e. each Product has an Account_Id

If you want a many to many relationship (and create an intermediary table), the following should work

class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Account> Accounts { get; set; }
}

class Account
{        
    public int Id { get; set; }
    public string Name { get; set; }
    public virtual ICollection<Product> Products { get; set; }
}
answered 2012-01-19T14:04:57.037
1
        public AccountProductsMap()
    {
        this.ToTable("AccountProducts");
        this.HasKey(cr => cr.Id);

        this.HasMany(cr => cr.Account)
            .WithMany(c => c.Products)
            .Map(m => m.ToTable("AccountProducts_Mapping"));
    }
answered 2012-01-19T14:07:13.370

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