这是实现与EF代码首先多对多关系的集合的方法吗？

Question

I have a situation where the code I've arrived at doesn't match any examples I find so I wonder if I'm missing something.

Basically, I want an EF code first Entity that contains a collection of Entities participating in a many-to-many relationship.

Then, I'd like to be able to:

• Add to collection at the same time as creating an entity
• Not get a warning about accessing a virtual member from constructor

Here's what I have:

public class NotificationUser
{
    private ICollection<NotificationUserGroup> _userGroups = new HashSet<NotificationUserGroup>();

    public int UserId { get; set; }

    public string UserName { get; set; }

    public bool IsActive { get; set; }

    public virtual ICollection<NotificationUserGroup> UserGroups
    {
        get { return _userGroups; }
        set { _userGroups = value; }
    }
}

Is there a better/different way to accomplish my goal?

Answer 1

This example might help

public class NotificationUser
{
    public NotificationUser()
    {
        UserGroups = new HashSet<NotificationUserGroup>();
    }

    public int NotificationUserId { get; set; }
    public string UserName { get; set; }
    public bool IsActive { get; set; }
    public virtual ICollection<NotificationUserGroup> UserGroups { get; set; }
}

public class NotificationUserGroup
{
    public int NotificationUserGroupId { get; set; }
    public string GroupName { get; set; }
}

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

    }
    public DbSet<NotificationUser> NotificationUsers { get; set; }
    public DbSet<NotificationUserGroup> NotificationUserGroup { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        Database.SetInitializer(new DropCreateDatabaseAlways<Context>());

        using (var ctx = new Context())
        {
            var user = new NotificationUser() { UserName = "Name1" };
            user.UserGroups.Add(new NotificationUserGroup() { GroupName = "Group1" });
            user.UserGroups.Add(new NotificationUserGroup() { GroupName = "Group2" });
            ctx.NotificationUsers.Add(user);

            ctx.SaveChanges();
        }

        using (var ctx = new Context())
        {
            foreach (var user in ctx.NotificationUsers)
            {
                foreach (var group in user.UserGroups)
                    Console.WriteLine("Group Id: {0}, Group Name: {1}, UserName: {2}", group.NotificationUserGroupId, group.GroupName,user.UserName);
            }

            foreach (var group in ctx.NotificationUserGroup)
            {
                Console.WriteLine("Group Id: {0}, Group Name: {1}", group.NotificationUserGroupId, group.GroupName);
            }
        }

        Console.ReadKey();
    }
}