Entity Framework: Attached Entities not Saving

Question

Hello:

I can't figure out why calling SaveChanges() on the following code results in no changes to the objects I attached:

public void Update()
{
AccountUser accountUser = new AccountUser();

// update
using (var db = new MedicalSystemDBEntity())
{
    var query = from user in db.AccountUsers   
                where user.id == this.UserID
                select user;

    if (query.Count() > 0)
    {
        accountUser = query.First();

        accountUser.AccountRoles.Load();
        accountUser.SecurityNavigationNodes.Load();

        // delete existing user roles before re-attaching
        if (accountUser.AccountRoles.Count > 0)
        {
            foreach (AccountRole role in accountUser.AccountRoles.ToList())
            {
                accountUser.AccountRoles.Remove(role);
            }
        }

        db.SaveChanges();

        // get roles to add
        List<int> roleIDs = new List<int>();

        foreach (UserRole r in this.AccountRoles)
        {
            roleIDs.Add(r.RoleID);
        }

        var roleEntities = from roles in db.AccountRoles
                           where roleIDs.Contains(roles.id)
                           select roles;

        accountUser.AccountRoles.Attach(roleEntities);

        accountUser.username = this.Username;
        accountUser.firstname = this.FirstName;
        accountUser.middlename = this.MiddleName;
        accountUser.lastname = this.LastName;
        accountUser.enabled = this.Enabled;

        if (this.LastActivityDate != null || this.LastActivityDate != DateTime.MinValue)
            accountUser.lastactivitydate = this.LastActivityDate;

        db.SaveChanges();
    }
}

}

In the debugger, I see that the correct roleEntities are being loaded, and that they are valid objects. However, if I use SQL Profiler I see no UPDATE or INSERT queries coming in, and as a result none of my attached objects are being saved.

Answer 1

Off the top of my head, shouldn't you do SaveChanges() after you've removed the roles from the account? Aren't you just removing the roles attached to the user, then reattaching the same ones? Since its saving the changes, nothing would have changed would it?

Answer 2

They're not saving because you change the entities before attaching them. Changes are tracked by the context (usually), so changes to detached entities aren't tracked. Hence, nothing to save.