The .NET Framework contains components that present standard Open/Save dialog boxes, which you can use in your applications, but you can not extend these dialogs, can not add custom controls as many applications add preview pane. Moreover, you can not inherit from Open/Save dialog components since they are sealed (Not Inheritable in Visual Basic). Preview dialogs library contains same dialogs with image preview box. You can set properties values at design-time and easily change image in preview box at run time.