Unable to save many-to-many relationship - entity-framework

Question

I have the following tables/views
Users (View)
-> UserId
-> Name
Roles (Table)
-> RoleId
-> Name
UserRoles (Table)
-> UserId
-> RoleId
and the classes
public class Role{
public int RoleId{get;set}
public string Name{get;set}
}
public class User{
public int UserId{get;set}
public string Name{get;set}
public ICollection<Role> Roles{get;set}
}
and the save method
using (var helper = new DbContext())
{
helper.Users.Attach(user);
helper.SaveChanges();
}
As you can see above, the Users is a view and UserRoles is a mapping table. I am able to retrieve User entities along with the mapped Roles. But while saving it is not throwing any exceptions nor is it saving. I tried checking the db using profiler and it is not even hitting the db.
Since Users is a view I don't want to save the User entity but only the changes made in the Roles collection.

Answer 1

This cannot save anything. Attach puts the whole object graph into the context, but in state Unchanged. If all objects in the context are unchanged SaveChanges won't issue any command to the DB (because for EF nothing has changed).
If you want to make changes which EF recognizes as such you must first attach the object which represents the state in the Db and then make your changes, something like:
using (var helper = new DbContext())
{
helper.Users.Attach(user);
helper.Roles.Attach(myNewRole);
user.Name = myNewName;
user.Roles.Add(myNewRole);
// etc.
helper.SaveChanges();
}
Alternatively you can mark the user as modified:
helper.Entry(user).State = EntityState.Modified;
But I believe this only affects scalar properties of the entity and it doesn't solve the problem to add a new role to the user.