Error 2 'System.Data.DataRow' does not contain a definition for 'Item' and no extension method 'Item' accepting a first argument of type 'System.Data.DataRow' could be found (are you missing a...

using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Collections;
using System .Collections.Generic ;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.IO;
using System.Data.OleDb;
using System.ComponentModel;
 
public partial class _Default : System.Web.UI.Page
{
    //class Point  { double X, Y; }
    DataTable dt = new DataTable();
    //int[][] polygon=new int[][];
    protected void Page_Load(object sender, EventArgs e)
    {
 
    }
    protected void btnSubmit_Click(object sender, EventArgs e)
    {
        string connectionString = "";
        if (FileUpload1.HasFile)
        {
            string fileName = Path.GetFileName(FileUpload1.PostedFile.FileName);
            string fileExtension = Path.GetExtension(FileUpload1.PostedFile.FileName);
            string fileLocation = Server.MapPath("~/App_Data/" + fileName);
            FileUpload1.SaveAs(fileLocation);
            if (fileExtension == ".xls")
            {
                connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + fileLocation + ";Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=2\"";
            }
            else if (fileExtension == ".xlsx")
            {
                connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileLocation + ";Extended Properties=\"Excel 12.0;HDR=Yes;IMEX=2\"";
            }
            OleDbConnection con = new OleDbConnection(connectionString);
            OleDbCommand cmd = new OleDbCommand();
            ArrayList List = new ArrayList();
            cmd.CommandType = System.Data.CommandType.Text;
            cmd.Connection = con;
            OleDbDataAdapter dAdapter = new OleDbDataAdapter(cmd);
            DataTable dtExcelRecords = new DataTable();
            con.Open();
            DataTable dtExcelSheetName = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
            string getExcelSheetName = dtExcelSheetName.Rows[0]["Table_Name"].ToString();
            cmd.CommandText = "SELECT * FROM [" + getExcelSheetName + "]";
            dAdapter.SelectCommand = cmd;
            dAdapter.Fill(dtExcelRecords);
            if (Session["dtInSession"] != null)
            {
                dt = (DataTable)Session["dtInSession"];
            }
            for (int i = 0; i < dtExcelRecords.Rows.Count; i++)
            {
               //int result;
                //if you want to get the string
              DataRow thisRow = (DataRow)dtExcelRecords.Rows[i];
               DataTable dt = new DataTable();
        dt.Columns.Add("X", typeof(int));
        dt.Columns.Add("Y", typeof(int));
                txtArea .Text = (CalculatePolygon_Area(dt)).ToString();
            }
        }
    }

    public double CalculatePolygon_Area(DataTable Poly_Table)
    {
        double Poly_Area1;
        double Poly_Area2;
        double Poly_Area;
        int i;
        int Count;
        Count = (Poly_Table.Rows.Count - 1);
        i = 0;
        Poly_Area = 0;
        Poly_Area1 = 0;
        Poly_Area2 = 0;
        
        for (i = 0; (i <= (Poly_Table.Rows.Count - 1)); i++) 
        {
            if ((i == Count)) 
            {
  am getting error here             // Poly_Area1 = (Poly_Area1 
                            + (Poly_Table.Rows[i].Item[0] * Poly_Table.Rows[0].Item[1]));
                Poly_Area2 = (Poly_Area2 
                            + (Poly_Table.Rows[i].Item[1] * Poly_Table.Rows[0].Item[0]));
            }
            else 
            {
   am getting error here            // Poly_Area1 = (Poly_Area1 
                            + (Poly_Table.Rows[i].Item[0] * Poly_Table.Rows[(i + 1)].Item[1]));
                Poly_Area2 = (Poly_Area2 
                            + (Poly_Table.Rows[i].Item[1] * Poly_Table.Rows[(i + 1)].Item[0]));
            }
        }
        Poly_Area = ((Poly_Area1 - Poly_Area2) 
                    / 2);
        return Poly_Area;
    }
    }