Bdtjtk

I want to create a many-to-many relationship with Fluent-API and to add entities to the database.

Here is my code so far:

class Program

{

    static void Main(string args)

    {

        Bar bar = new Bar

        {

            Id = 1,

            Street = "BarStreet"

        };



        Foo foo1 = new Foo

        {



            Name = "FooName1",

            Bars = { bar },

        };



        Foo foo2 = new Foo

        {

            Name = "FooName2",

            Bars = { bar },

        };





        using (SandBoxModelContext db = new SandBoxModelContext())

        {

            Bar existingBar = db.Bar.FirstOrDefault(b => b.Id == bar.Id);

            if (existingBar != null)

            {

                foo1.Bars.ToList()[0] = existingBar;

                foo1.Bars.ToList()[0] = existingBar;

            }



            db.Foo.Add(foo1);

            db.Foo.Add(foo2);

            db.SaveChanges();

        }



        Console.ReadLine();

    }

}



class Foo

{

    internal int Id { get; set; }

    internal string Name { get; set; }



    internal virtual ICollection<Bar> Bars { get; set; }



    public Foo()

    {

        Bars = new HashSet<Bar>();

    }

}



class Bar

{

    internal int Id { get; set; }

    internal string Street { get; set; }



    internal virtual ICollection<Foo> Foos { get; set; }



    public Bar()

    {

        Foos = new HashSet<Foo>();

    }

}

When I first run the application everything works fine. I get two foos and one bar, which are related to each other through the joining table FooBar.

|    Foo    | |    Bar      | |  FooBar   |

|Id|  Name  | |Id| Street   | |FooId|BarId|

|-----------| |-------------| |-----------|

| 1|FooName1| | 1|BarStreet1| |  1  |  1  |

| 2|FooName2|                 |  2  |  1  |

But the second time I get two additional foos, which is fine, but I get also a second bar-record.

|    Foo    | |    Bar      | |  FooBar   |

|Id|  Name  | |Id| Street   | |FooId|BarId|

|-----------| |-------------| |-----------|

| 1|FooName1| | 1|BarStreet1| |  1  |  1  |

| 2|FooName2| | 2|BarStreet1| |  2  |  1  |

| 3|FooName1|                 |  3  |  2  |

| 4|FooName2|                 |  4  |  2  |

How can I add a relationship to an existing record?
In this case I want to add new Foos and connect them to an existing Bar-record.

Here my FluentApi-Configuration:

#region Foo

modelBuilder.Entity<Foo>()

    .Property(f => f.Id)

    .HasColumnType("int");

modelBuilder.Entity<Foo>()

    .HasKey(f => f.Id);

modelBuilder.Entity<Foo>()

    .Property(f => f.Name)

    .HasColumnType("nvarchar(max)");

#endregion



//many-to-many configuration

modelBuilder.Entity<Foo>()

    .HasMany(f => f.Bars)

    .WithMany(b => b.Foos)

    .Map(fb =>

    {

        fb.MapLeftKey("FooId");

        fb.MapRightKey("BarId");

        fb.ToTable("FooBar");

    });





#region Bar

modelBuilder.Entity<Bar>()

    .Property(f => f.Id)

    .HasColumnType("int");

modelBuilder.Entity<Bar>()

    .HasKey(f => f.Id);

modelBuilder.Entity<Bar>()

    .Property(f => f.Street)

    .HasColumnType("nvarchar(max)");

#endregion