Many-to-many mapping table

Question

From examples that I have seen online and in a Programming Entity Framework CodeFirst book, when you have a collection on both classes EF would create a mapping table such as MembersRecipes and the primary key from each class would link to this table.

However when I do the below, I instead get a new field in the Recipes table called Member_Id and a Recipe_Id in the Members table.

Which only creates two one-to-many relationships, but not a many-to-many so I could have Member 3 linked to Recipes (4,5,6) and Recipe 4 linked to Members (1,2,3) etc.

Is there a way to create this mapping table? and if so how do you name it something else such as "cookbooks" ?

Thanks

    public abstract class Entity {         [Required]         public int Id { get; set; }     }         public class Member : Entity {         [Required]         public string Name { get; set; }          public virtual IList<Recipe> Recipes { get; set; }     }      public class Recipe : Entity {           [Required]         public string Name { get; set; }          [ForeignKey("Author")]         public int AuthorId { get; set; }         public virtual Member Author { get; set; }              ....          public virtual IList<Member> Members { get; set; }     } 

UPDATE: Below is another approach I have tried which doesn't use the Fluent API and replaces the AuthorId & Author on Recipe with an owner flag, I have also renamed the below example from Cookbooks to MembersRecipes, this also fixes my issue similar to the answer but as mentioned has further implications.

public class MembersRecipes {      [Key, Column(Order = 0)]     [ForeignKey("Recipe")]     public int RecipeId { get; set; }     public virtual Recipe Recipe { get; set; }      [Key, Column(Order = 1)]     [ForeignKey("Member")]     public int MemberId { get; set; }     public virtual Member Member { get; set; }      public bool Owner { get; set; } } 

and in Recipe & Member classes I changed the collections to

public virtual IList<MembersRecipes> MembersRecipes { get; set; } 

Answer 1

Do this on your DbContext OnModelCreating:

protected override void OnModelCreating(DbModelBuilder modelBuilder) {         modelBuilder.Entity<Recipe>()         .HasMany(x => x.Members)         .WithMany(x => x.Recipes)     .Map(x =>     {         x.ToTable("Cookbooks"); // third table is named Cookbooks         x.MapLeftKey("RecipeId");         x.MapRightKey("MemberId");     }); } 

You can do it the other way around too, it's the same, just another side of the same coin:

modelBuilder.Entity<Member>()     .HasMany(x => x.Recipes)     .WithMany(x => x.Members) .Map(x => {   x.ToTable("Cookbooks"); // third table is named Cookbooks   x.MapLeftKey("MemberId");   x.MapRightKey("RecipeId"); }); 

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Further examples:

http://www.ienablemuch.com/2011/07/using-checkbox-list-on-aspnet-mvc-with_16.html

http://www.ienablemuch.com/2011/07/nhibernate-equivalent-of-entity.html

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UPDATE

To prevent cyclical reference on your Author property, aside from above, you need to add this:

modelBuilder.Entity<Recipe>()     .HasRequired(x => x.Author)     .WithMany()     .WillCascadeOnDelete(false); 

Idea sourced here: EF Code First with many to many self referencing relationship

The core thing is, you need to inform EF that the Author property(which is a Member instance) has no Recipe collections(denoted by WithMany()); that way, cyclical reference could be stopped on Author property.

These are the created tables from the Code First mappings above:

CREATE TABLE Members(     Id int IDENTITY(1,1) NOT NULL primary key,     Name nvarchar(128) NOT NULL );   CREATE TABLE Recipes(     Id int IDENTITY(1,1) NOT NULL primary key,     Name nvarchar(128) NOT NULL,     AuthorId int NOT NULL references Members(Id) );   CREATE TABLE Cookbooks(     RecipeId int NOT NULL,     MemberId int NOT NULL,     constraint pk_Cookbooks primary key(RecipeId,MemberId) );