# OnClientSelectedTabChanging

The **OnClientSelectedTabChanging** client-side event occurs when the user clicks on a ribbonbar tab, before the ribbonbar responds to the mouse click.

The event handler receives two parameters:

1. The instance of the ribbonbar firing the event.

2. An eventArgs parameter containing the following methods:

   * **get_tab()** returns a reference to the ribbonbar tab which is about to be selected.

   * **get_previouslySelectedTab()** returns a reference to the currently selected tab.

   * **get_domEvent()** returns the DOM event object.

   * **set_cancel()** lets you cancel the event and prevent changing the selected tab.

## See Also

* [Client-side Programming Overview](https://www.telerik.com/products/aspnet-ajax/documentation/controls/ribbonbar/client-side-programming/overview)

* [Client-side Events Overview](https://www.telerik.com/products/aspnet-ajax/documentation/controls/ribbonbar/client-side-programming/events/overview)