How do I upload an excel file to ASP.NET

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.OleDb;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.OleDb;
using System.Configuration;
using System.IO;
using System.Data;

namespace Interfaz
{
    public partial class _Default : Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            string filePath = ConfigurationManager.AppSettings["FilePath"].ToString();
            string filename = string.Empty;
            if (FileUpload1.HasFile)
            {
                try
                {
                    string[] allowFile = {".xls",".xlsx" };
                    string FileExt = System.IO.Path.GetExtension(FileUpload1.PostedFile.FileName);
                    bool isValidFile = allowFile.Contains(FileExt);
                    if (!isValidFile)
                    {
                        lblMsg.ForeColor = System.Drawing.Color.Red;
                        lblMsg.Text = "Porfavor solo suba archivos de Excel";
                    }
                    else
                    {
                        //Upload only less or equal to 1 mb
                        /*int FileSize = FileUpload1.PostedFile.ContentLength;
                        if (FileSize<=1048576)
                        {

                        }*/
                        filename = Path.GetFileName(Server.MapPath(FileUpload1.FileName));
                        FileUpload1.SaveAs(Server.MapPath(filePath) + filename);
                        OleDbConnection con = null;
                        if (FileExt==".xls")
                        {
                            grid.Visible = true;
                            con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+filePath+";Extended Properties=Excel 8.0;");
                        }
                        if (FileExt == ".xlsx")
                        {
                            grid.Visible = true;
                            con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.12.0;Data Source=" + filePath + ";Extended Properties=Excel 12.0;");
                        }
                        con.Open();
                        DataTable dt = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables,null);
                        String[] sheetNames = new String[dt.Rows.Count];
                        /*int i = 0;
                        foreach (DataRow row in dt.Rows)
                        {
                            cb.Items.Add(row["TABLE_NAME"].ToString());
                            i++;
                        }*/
                        OleDbCommand ExcelCommand = new OleDbCommand(@"SELECT * FROM ["+sheetNames+@"]",con);
                        OleDbDataAdapter ExcelAdapter = new OleDbDataAdapter(ExcelCommand);
                        DataSet ExcelDataSet = new DataSet();
                        con.Close();
                        grid.DataSource = ExcelDataSet;
                        grid.DataBind();
                    }
                }
                catch (Exception ex) { }
            }
        }
    }
}