code: function event_update(winjsComponent, propName, oldValue, newValue) {
              if (oldValue !== newValue) {
                  winjsComponent.winControl[propName.toLowerCase()] = newValue;
              }
          }
docs: Can't set options in preCtorInit for events. The problem is WinJS control options use a different code path to hook up events than the event property setters. Consequently, setting an event property will not automatically unhook the event listener that was specified in the options during initialization. To avoid this problem, always go thru the event property setters.