converting multiple LINQ queries into 1?
===

Is it possible to convert this code into one LINQ query. I could have sworn I had done something like this before, but I cannot figure out where I might that code might be. I want to perform a sub query and modify the values of the selected items if one list has values from another.

    var allInstructors = _instructorService.GetAllNonGuestInstructors();
    var selectInstructors =
                        allInstructors.Select(
                            i =>
                            new SelectListItem() { Text = i.User.ToFullName(), Value = i.Id.ToString() }).ToList();
    
                    foreach (var selectedItem in schedule.Instructors.Select(instructior1 => selectInstructors.FirstOrDefault(s => s.Value == instructior1.Id.ToString())).Where(selectedItem => selectedItem != null))
                    {
                        selectInstructors.Remove(selectedItem);
                        selectedItem.Selected = true;
                        selectInstructors.Add(selectedItem);
                    }