UNdo در Memo وmemoField

Memo1.Perform(EM_UNDO, 0, 0);

تشخیص UNdo (یعنی متن تغییر کرده)

ButtonUndo.Enabled := Memo1.Perform(EM_CANUNDO, 0, 0);
ButtonUndo.Enabled := Memo1.CanUndo; 

پاک کردن حافظه Undo

  Memo1.Perform(EM_EMPTYUNDOBUFFER, 0, 0);

Memo1.ClearUndo; // in Delphi 4 or higher