Add Many-to-Many Entity Framework
Users objUser = new Users();

objUser.name = itemUsers.name.Trim();
objUser.email = itemUsers.email.Trim();
objUser.password = Util.HashString("12345");
objUser.effdt = DateTime.Now;

objData.Users.AddObject(objUser);

foreach (var itemMenu in itemUsers.Menu)
{
    objData.ObjectStateManager.ChangeObjectState(itemMenu, EntityState.Unchanged);
}

affRows = objData.SaveChanges();