EF Code First many-to-many: how to specify name of th third table and add some other properties to it?

Question

I need to implement the many-to-many relationship in the Entity Framework Code First, and map this relationship to the third table. And I want to add to this table some other fields such as autoincremented Id and the AppointmentDateTime for exaple:

public class User {
    public int Id { get; set; }
    // some other properties ......
    public virtual List<Role> Roles { get; set; }
}

public class UserTypeConfiguration : EntityTypeConfiguration<User> {
    public UserTypeConfiguration() {
        HasKey(k => k.Id);
        Property(p => p.Email).IsRequired();
        //[∞ — ∞]
        HasMany<Role>(u => u.Roles).WithMany(r => r.Users).Map(m => m.MapLeftKey("UserId").MapRightKey("RoleId").ToTable("UserRoles"));
    }
}

But Entity Framework generates a table with the wrong name that which I have passed, and wrong names navigation proiperties I have passed to the mapping.

The name of table "RoleUsers" and the names of navigation proiperties are "User_Id" and "Role_Id".

How to implement correct names of mapping and how to add some other properties to the UserRoles table?

Answer 1

Since you need to add additional properties to describe the relationship, you have to consider many-to-many association as two one-to many ones:

public class User
{
    // other properties omitted
    public virtual List<UserRole> UserRoles { get; set; }
}

public class Roles
{
    // other properties omitted
    public virtual List<UserRole> UserRoles { get; set; }
}

public class UserRole
{
    public int Id { get; set; }
    public DateTime AppointmentDateTime { get; set; }
    public int UserId { get; set; }
    public User User { get; set; }
    public int RoleId { get; set; }
    public Role Role { get; set; }
}

Configuration:

public class UserRoleConfiguration : EntityTypeConfiguration<UserRole> 
{
    public UserRoleConfiguration()
    {
        // scalar properties config omitted
        HasRequired(_ => _.User)
            .WithMany(_ => _.UserRoles)
            .HasForeignKey(_ => _.UserId);

        HasRequired(_ => _.Role)
            .WithMany(_ => _.UserRoles)
            .HasForeignKey(_ => _.RoleId);

        ToTable("UserRoles");
    }
}