请帮忙解决下列问题.急!

这是导出数据到Excel按钮的代码:
Response.Clear();
        Response.BufferOutput = true;
        Response.Charset = "GB2312";
        Response.AppendHeader("Content-Disposition", "attachment;filename = 订单.xls");
        Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");
        Response.ContentType = "application/ms-excel";
        string strExcelHeader = string.Empty;
        string strExcelItems;
        if (ViewState["comstr"] != null)    // 取前面查询用的SQL语句
        {
            // 取得各列标题，各标题之间以\t分割，最后一个列标题后加回车符
            strExcelHeader = "No\tDate\tP/N\tDescription\tQty\tResult\t\n";
            // 向HTTP输出流中写入取得的数据信息
            Response.Write(strExcelHeader);

            // 逐行处理查询结果数据
            ITDBHandle itDbHandle = new ITDBHandle();
            itDbHandle.QueryString = ViewState["comstr"].ToString();
            SqlDataReader reader = itDbHandle.ExecuteDataReader();
            while (reader.Read())
            {
                strExcelItems = string.Empty;
                strExcelItems += reader["SeqId"].ToString() + "\t";
                strExcelItems += reader["ReportIssueDate"].ToString() + "\t";
                strExcelItems += reader["Item"].ToString() + "\t";
                strExcelItems += reader["Description"].ToString() + "\t";
                strExcelItems += reader["Quantity"].ToString() + reader["Model"].ToString() + "\t";
                //strExcelItems += reader["Result"].ToString() + "\t";
                //strExcelItems += reader["OrderDate"].ToString() + "\t";
                //strExcelItems += reader["IsValid"].ToString() + "\t";
                strExcelItems += reader["Result"].ToString() + "\n";
                Response.Write(strExcelItems);
            }
            reader.Close();
            Response.End();
        }
出现错误如附件: --------------------编程问答-------------------- 错误提示如下:
编译器错误信息: CS0246: 找不到类型或命名空间名称“ITDBHandle”(是否缺少 using 指令或程序集引用?) --------------------编程问答-------------------- ITDBHandle这个应该是别人写的一个类! --------------------编程问答-------------------- 想问一下现在该怎样做?

补充：.NET技术 ,  C#