procedure TForm1.Button1Click(Sender: TObject);
begin
if edit1.text<>'' and listbox1.Items.IndexOf(edit1.text)<>-1 then
listbox1.Items.Add(edit1.text);
end;
begin
if edit1.text<>'' and listbox1.Items.IndexOf(edit1.text)<>-1 then
listbox1.Items.Add(edit1.text);
end;
begin
if (edit1.text<>'') and (listbox1.Items.IndexOf(edit1.text)<>-1) then
listbox1.Items.Add(edit1.text);
end;