TCommonDialog = class(TComponent)
class PASCALIMPLEMENTATION TCommonDialog : public System::Classes::TComponent
TCommonDialog is the ancestor of all components that represent Windows common dialog boxes.
TCommonDialog is an abstract class that represents Windows common dialog boxes. Its descendants handle such tasks as finding and opening files, setting fonts and colors, and printing. The dialogs do not appear at runtime until activated by a call to the Execute method. Except for TFindDialog and TReplaceDialog, these dialogs are all modal.
The TCommonDialog descendants are nonvisual components that generate a single function call to COMMDLG.DLL, and are therefore less easily modified than other components. New components that encapsulate common-dialog functions should descend from TCommonDialog. Most other dialog boxes should descend from TForm.