C# 阅读器封闭时尝试调用 MetaData 无效

C# 阅读器关闭时尝试调用 MetaData 无效
        public DataSet RunProcReturn(string procName)
        {
            DataSet ds = new DataSet();
            try
            {
                SqlDataAdapter dap = CreateDataAdaper(procName, null);
                dap.Fill(ds, "tbName");
                return ds;
            }
            catch
            {
                Close();
                return ds;

            }          
        }
  private SqlDataAdapter CreateDataAdaper(string procName, SqlParameter[] prams)
        {
            Open();
            SqlDataAdapter dap = new SqlDataAdapter(procName, strConn);
            dap.SelectCommand.CommandTimeout = 180;   
            dap.SelectCommand.CommandType = CommandType.Text;  //执行类型：命令文本
             if (prams != null)
            {
                foreach (SqlParameter parameter in prams)
                    dap.SelectCommand.Parameters.Add(parameter);
            }
            return dap;
        }

  public void Open()
        {
            // 打开数据库连接
            Close();
            if (strConn == null)
            {
                strConn = new SqlConnection(connStr);
            }
            if (strConn.State == System.Data.ConnectionState.Closed)
                strConn.Open();