Question

I have

User:
 -ID
 -Name

Badge
 -ID
 -Name (E.G "User has made 100 posts", the same relationship as Stackoverflow)

So I’ve realised I need a third table, (as badges are defined in the DB aswell so I’ve created:

UserBadge
 -ID
 -User
 -Badge

So now in my User class I have

List<UserBadge> Badges;

Problem is, I’m going

Users.Find(1).Badges.Where(x => x.User == user && x.Badge = badgeIWant)
     .FirstOrDefault();

(Or something similar) Because… EF doesn’t have the intelligence (I’m guessing) to automatically know that “Badges” should only include the ones where the User matches.

How should I do this? Was thinking I could have a custom getter for Badges, that has that LINQ conditional in it…

Answer 1

This is EF 4.3 code first:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Entity;

namespace ConsoleApp
{
    public class User
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public virtual ICollection<Badge> Badges { get; set; }
    }

    public class Badge
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public virtual ICollection<User> Users { get; set; }
    }

    public class Context : DbContext
    {
        public Context()
            : base("Votes")
        {

        }
        public DbSet<User> Users { get; set; }
        public DbSet<Badge> Badge { get; set; }
    }


    class Program
    {
        static void Main(string[] args)
        {
            Context context = new Context();
            User user = context.Users.Include("Badges").Where(u => u.ID == 1).SingleOrDefault();
            if(user != null)
            {
                //write your code.
            }

            Console.ReadKey();
        }
    }
}

I’ve tested it and this should work. This would typically be a many to many relationship because User can have many badges and 1 badge can belong to many users. If you run this code, you will find EF creates BadgeUsers table with BadgeID and UserID as foreign keys. From there on you can query and EF knows which badges you talking about.