Occurs when the user makes a change within the control.
Use this event to write code that performs the action when a user types in the Edit control or edit portion of the ComboBox control, selects a new image in an ImageBox control (via selecting a file or using the camera), or selects a new date in the DateTime control. This event only occurs for ComboBox, Imagebox, Edit, and DateTime controls. In certain cases (for example, when a slider control is linked to a buddy edit control), a control's OnChange event will fire after the page's OnLoad event fires, but before the form's OnLoad event fires. It is the developer's responsibility to handle these cases in thier scripts.