You create a custom control named OrderForm.  You write the following code segment.  public delegate void  CheckOrderFormEventHandler(EventArgs e);  private static readonly object CheckOrderFormKey  = new object（　）;  public event CheckOrderFormEventHandler  CheckOrderForm {  add {  Events.AddHandler(CheckOrderFormKey, value);  }  remove {  Events.RemoveHandler(CheckOrderFormKey,  value);  }  }  You need to provide a method that enables the OrderForm control to raise the CheckOrderForm event.  Which code segment should you use?（）