c# 将Datatable数据导出到Excel表格中

     　public FileResult GetExcelFile()
        {
            if (Session["beginDate"] != null)
            {
                string bdate = Session["beginDate"].ToString();
                DateTime ld = Convert.ToDateTime(Session["lastDate"].ToString());
                DateTime ldate = ld.AddDays(1);
                string lldate = ldate.ToString("yyyy-MM-dd");
                int ptkey = Convert.ToInt32(Session["Process_PTR"]);
                string proceSql = "select * from Assay_Process where RKEY="+ptkey;
                DataTable proceDt = SqlHelper.QueryTable(proceSql);
                IDataParameter[] iDataTitle = new SqlParameter[3];
                iDataTitle[0] = new SqlParameter("@BeginDate", bdate);
                iDataTitle[1] = new SqlParameter("@LastDate", lldate);
                iDataTitle[2] = new SqlParameter("@RKEY", ptkey);
                DataSet dtTitle = SqlHelper.RunProceduresByParameter("pro_GetAssalyInfoByExportPrint", iDataTitle);
                DataTable dt = dtTitle.Tables[0];
                string outStr = ExcelExport.outExcel(dt);
                byte[] fileContents = Encoding.UTF8.GetBytes(outStr.ToString());
                return File(fileContents, "application/ms-excel", "" + proceDt.Rows[0]["ProcessName"].ToString().Trim() + "化验单据(" + bdate.Trim() + "-" + lldate.Trim() + ").xls");
            }
            else
            {
                string qua_no = Session["quano"].ToString();
                IDataParameter[] iDataTitle = new SqlParameter[1];
                iDataTitle[0] = new SqlParameter("@Qua_no", qua_no);
                DataSet dtTitle = SqlHelper.RunProceduresByParameter("pro_GetAssalyInfoByQua_No", iDataTitle);
                DataTable dt = dtTitle.Tables[0];
                string outStr = ExcelExport.outExcel(dt);
                byte[] fileContents = Encoding.UTF8.GetBytes(outStr.ToString());
                return File(fileContents, "application/ms-excel", "化验单据(" + qua_no.Trim()+ ").xls");
            }
        }