The Edit-Combo Builder
The Edit-Combo Builder is used to construct Edit Combo style Lookup controls.
The 'NotInList' event fires when the user enters a value into an Auto-suggest or Edit-combo control and the value entered is not is the list of available choices for the control.
The primary use case for this event is to allow the developer to add code to the component to add the value that was entered into the control into the table on which the control choices are based so that the next time the user visits the control the value entered will be in the pick list for that control.
Dropdownbox controls allow you to specify that the stored value is different from the display value. For example, the control might display a 'ProductName' but the stored value in the control might be the 'ProductId'.
Edit-combo box controls can now also be configured to store a different value than their display value, just like a Dropdownbox control.
The benefit of using an Edit-combo control over a Dropdownbox control is that you can display multiple columns of data in the choice list and you can dynamically populate and filter the choices in the list with an Ajax callback every time the control is opened.