字符串截取，SubString

procedure TForm12.btn1Click(Sender: TObject);

var

  wokao: string;

begin

  wokao := 'abcde_fg';

  ShowMessage(IntToStr(wokao.IndexOf('_')));//

  ShowMessage(wokao.Substring(,wokao.IndexOf('_')));//abcde

end;