Available control system from .NET Core 6

I want to have parking available system. So I have boolean variable which is Status. And I set default variable is true. It means parking slot is available.

After added data Status is false. But it doesn't work. It still save same data. How can I have control system for available or not?

This is my model

 public Boolean Status { get; set; } = true;

This is my if else control

  if (obj.Status == true)
  {
      _db.Bookings.Add(obj);
      obj.Status = false;
      _db.SaveChanges();

      TempData["success"] = "Booking created successfully";
  }
  else
  {
      TempData["error"] = "This slot is already booked for " + obj.PickHours + " hours";
      return RedirectToAction("Index");
  }

  return View(obj);