This page contains a user control.  
            The user control, in the OnInit, creates six textboxes and adds a TextChanged handler to each one.
            The user control also has a public event, FieldChanged, that can be set by the page that adds the user control.  
            The TextChanged handler calls the event of the user control, FieldChanged, if it is assigned to something.  
            The user control has no idea what the owner page has assigned FieldChanged event to, but it knows it does something.
            The owner page, in the OnInit, sets the necessary event handlers: one for the page PreRender, and another for the user control FieldChanged.
            The FieldChanged handler just increments a counter each time it is called.  
            And it is called, as set by the user control, each time a text box has changed values.
            The PreRender handler updates a label based on the counter.  
            It also updates the browser title by adding a new LiteralControl.