以下代码，因为没有显式的Dispose连接，return后，连接是否会立刻自动释放？
Broker broker = BrokerFactory.CreateBroker("xxx");
try
{
      string sql = "select xxx from xxx";
      DataTable table = broker.ExecuteQuery(sql, new object[] { usrtype });
      if (table.Rows.Count > 0)
      {
            return table.Rows[0]["aaa"].ToString();
      }
      return string.Empty;
}
catch (Exception ex)
{
      throw new Exception(ex);
}
finally
{
      broker.Dispose();
}