Entity framework many to many keeps adding extra record - entity-framework

Question

I'm trying to add a new record to the link table using entityframework code first. What I have is a many to many on User and Role. The scenario I have is that when I'm changing a role for the user, I delete all their previous roles and add the new roles as follows:
//Delete all associated roles for user
var roleUser = db.Users.Include(r => r.Roles).FirstOrDefault(u => u.UserId == user.UserId);
var usersRoles = roleUser.Roles;
usersRoles.ForEach(role => roleUser.Roles.Remove(role));
//add the new roles
roleUser.Roles.AddRange(detachedUser.Roles);
db.SaveChanges();
So it removes them perfectly. But when adding new roles, it doesn't only add it to the link table but also the Role table. A completely new role gets added without a RoleName. user.Roles would contain an item with the following data:
RoleId;//1 <-- this Id exists in the database already but yet still it creates one instead of a linktable record.
RoleName;//null
How do I prevent EF from adding a whole new record and just add a record to the link table?
Update: I ended up doing this:
var roleUser = db.Users.Include(r => r.Roles).FirstOrDefault(u => u.UserId == user.UserId);
var roles = db.Roles;
foreach (var role in roles)
{
if (user.Roles.Any(r => r.RoleId == role.RoleId))
{
roleUser.Roles.Add(role);
}
else
{
roleUser.Roles.Remove(role);
}
}
db.SaveChanges();

Answer 1

try to save before adding new roles to the user
//Delete all associated roles for user
var roleUser = db.Users.Include(r => r.Roles).FirstOrDefault(u => u.UserId == user.UserId);
var usersRoles = roleUser.Roles;
usersRoles.ForEach(role => roleUser.Roles.Remove(role));
db.SaveChanges();
roleUser.Roles.AddRange(user.Roles); //add the new roles
db.SaveChanges();
Edit:
Have a look at this :
roleUser.Roles.AddRange(user.Roles); //add the new roles
where do user.Roles come from ?

Answer 2

I think the problem you have is that you need to attach your Roles before adding them to the user.
you also don't need to remove them all, simply remove those removed and then only add the new ones.

Answer 3

For each roll that you add you could try checking or setting the entity state. For example here I set the set to unchaged. This way it wont attempt to insert or update it.
myContext.Entry(roll).State = EntityState.Unchanged
More info here:
http://blogs.msdn.com/b/adonet/archive/2011/01/29/using-dbcontext-in-ef-feature-ctp5-part-4-add-attach-and-entity-states.aspx