Fires on the client side when the button loses input focus.
The LostFocus event's data class is ASPxClientEventArgs.
A button’s LostFocus event occurs on the client side before focus is moved from the button to another control within the same page. This event can be handled to perform specific client actions when the button loses focus.
Do not attempt to set focus from within the LostFocus event handler. Doing so can cause your application to stop responding.