Попробуйте: procedure TMainForm.UniTabSheet2Close(Sender: TObject; var AllowClose: Boolean); begin AllowClose := ((Sender as TUniTabSheet).CustomAttribs.Values['allowClose'] = 'true'); if not AllowClose then MessageDlg('Are you sure you want to close this tab?', mtConfirmation, [mbYes, mbNo], procedure (AComponent: TComponent; ARes: Integer) begin if ARes = mrYes then begin (Sender as TUniTabSheet).CustomAttribs.Values['allowClose'] := 'true';
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