Question

I’m very new at this, I’d really like some help with this problem:

First I already have a database, say I have 3 tables in this database: User, UserMapping, UserRole.
I generated a model with 3 class as follows:

public  class user
{
        public int UserID { get; set; }
        public string UserName { get; set; }

        public virtual ICollection<UserMapping> UserMappings { get; set; }
}

   public class UserMapping
    {
        public int UserMappingID { get; set; }
        public int UserID { get; set; }
        public int UserRoleID { get; set; }

        public virtual User User { get; set; }
        public virtual UserRole UserRole { get; set; }

    }

  public class UserRole
    {
        public int UserRoleID { get; set; }
        public string RoleName { get; set; }

        public virtual ICollection<UserMapping> UserMappings { get; set; }

    }

I want to create a new user, and add a User Role for the new user. User and User Role have no direct relationship. I want to make a view to create a new user, using the User model class with strongly-typed. How can I make a User Role for the user in this view?

Please help…! Thank you very much in advance.

Answer 1

You don’t need to create UserMapping entity by your self . Because when you specify your many to many relationship between User and UserRole EF will automatically create the relationship table UserUserRole relationship table for you.

  public  class User
     {
        public int UserID { get; set; }
        public string UserName { get; set; }

        public virtual ICollection<UserRole> UserRoles{ get; set; }
     }


  public class UserRole
    {
        public int UserRoleID { get; set; }
        public string RoleName { get; set; }

        public virtual ICollection<User> Users { get; set; }

    }

Then you can map the relationship table to the existing one,

protected override void OnModelCreating(ModelBuilder modelBuilder)
{

modelBuilder.Entity<User>().HasMany(u => u.UserRoles)
            .WithMany(r => r.Users )
            .Map(m =>
            {
                m.MapLeftKey("UserID");
                m.MapRightKey("UserRoleID");
                m.ToTable("YourExistinegTableName");
            });

}