Fires on the client side when the editor’s Design View Area loses input focus.
The LostFocus event's data class is ASPxClientEventArgs.
The LostFocus event occurs on the client side before focus is moved from the Design View Area to another control within the same page or to another element of the ASPxHtmlEditor (a toolbar button, for instance). This event can be handled to perform specific actions (for instance, to validate user input) when the ASPxHtmlEditor’s Design View Area loses focus.
Do not attempt to set focus from within the LostFocus event handler. Doing so can cause your application to stop responding.