Error while uploading a data from Excel read to datbase

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using System.Data.OleDb;
using System.Data;
using System.Collections;
using System.Configuration;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page 
{
    // Connection Establishment to the admin database 
    SqlConnection sqlcAdminConn = new SqlConnection(ConfigurationManager.ConnectionStrings["adminConnectionString"].ConnectionString);
    // variable for Excel Connection
    string connectionString = "";

   
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    // Button Click Event   
    protected void btnUpload_Click(object sender, EventArgs e)
    {
        // Variables to throw Exceptions manually 
        int a,b=100,c=0;    
        // Condition to check File availability
        if (FileUpload1.HasFile)
        {
            // Do not display warnibg when file is available
            lblWarning.Visible = false;
            string fileName = Path.GetFileName(FileUpload1.PostedFile.FileName);
            string fileExtension = Path.GetExtension(FileUpload1.PostedFile.FileName);
            string fileLocation = Server.MapPath("~/App_Data/" + fileName);
            FileUpload1.SaveAs(fileLocation);
            //Check whether file extension is xls or xslx
            try
            {
                // Condition to check File extension/version for 1997-2003
                if (fileExtension == ".xls")
                {
                    // Excel Connection string 
                    connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + fileLocation + ";Extended Properties=\"Excel 8.0;HDR=Yes;IMEX=2\"";
                    GridBinding();
                }
              
                // Condition to check File extension/version for slsx
                else if (fileExtension == ".xlsx")
                {
                    connectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileLocation + ";Extended Properties=\"Excel 12.0;HDR=Yes;IMEX=2\"";
                    GridBinding();
                }
                // File Extension other than xls/xlsx
                else
                {
                    // Exprssion to throw Exception
                    a = b / c;
                }
                //String strConnection = "Data Source=172.16.100.42;Initial Catalog=MySamplesDB;Integrated Security=True";
                sqlcAdminConn.Open();
                //file upload path
                string path = FileUpload1.PostedFile.FileName;
                //Create connection string to Excel work book
                string excelConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=Excel 12.0;Persist Security Info=False";
                //Create Connection to Excel work book
                OleDbConnection excelConnection = new OleDbConnection(excelConnectionString);
                //Create OleDbCommand to fetch data from Excel [StaffCode],[Date],[FirstIn],[LastOut],[TotalHrsFILO]
                OleDbCommand cmdExcel = new OleDbCommand("Select *  from [Sheet2$] where [Language]='EN' ", excelConnection);

                try
                {   
                    //Reader to load content from Excel sheet
                    OleDbDataReader dReader;
                    excelConnection.Open();
                    dReader = cmdExcel.ExecuteReader();
                    SqlBulkCopy sqlBulk = new SqlBulkCopy(sqlcAdminConn);
                    //Give your Destination table name
                    sqlBulk.DestinationTableName = "admin.dbo.SwipeCardData";
                    sqlBulk.WriteToServer(dReader);
                    excelConnection.Close();
                    lblWarning.Text = "File Uploaded Successfully";
                    lblWarning.Visible = true;

                }
                // if the data is already available
                catch (Exception ex)
                {
                    lblWarning.Text = ex.Message.ToString();
                        //"Data Already Uploaded for the Day";
                    lblWarning.Visible = true;
                }
            }
            // if the file format is other than xls/xlsx
            catch (Exception exFileFormat)
            {
                 lblWarning.Text = "File Compatibility Issue Select xls/xlsx format";
                 lblWarning.Visible = true;
            }
        }
        // If the file is not prasent file upload control
        else
        {
            // warning message to display  if file is not available
            lblWarning.Text = "* Select one Excel File to be Uploaded ";
            lblWarning.Visible = true;
        }
    }

    // Code to bind the grid view if data is available in xlx/xlsx file
    public void GridBinding()
    {
        //Create OleDB Connection and OleDb Command
        OleDbConnection con = new OleDbConnection(connectionString);
        OleDbCommand cmd = new OleDbCommand();
        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 [Sheet2$]";
        dAdapter.SelectCommand = cmd;
        dAdapter.Fill(dtExcelRecords);
        con.Close();
        GridView1.DataSource = dtExcelRecords;
        GridView1.DataBind();
    }
}