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procedure TForm1.Button1Click(Sender: TObject);
Var
i  : Integer;
begin
  for i:= 0 to combobox1.ItemIndex -1 do
  begin
    if combobox1.Items.IndexOf(edit1.text) > -1 then label1.Caption:='5' else label1.Caption:='0';
  end;
end;					

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procedure TForm1.Button1Click(Sender: TObject);
begin
  if Combobox1.Items.IndexOf(Edit1.Text) > -1 then
    ShowMessage(IntToStr(Combobox1.Items.IndexOf(Edit1.Text)))
  else
    ShowMessage('Nicht gefunden.');
end;