Question

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

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.