Error in reading a uploaded .xls excel file in asp.net

Question

Hi,

I have made a program where I read set of records from the database and then save it in a datagrid. From here I make the user download the file as a excel file.

Now the user make changes to the file and then upload it again and from here I read the uploaded .xls file and make the necessary changes in the DB.

The problem is whenever the user is uploading the updated excel file, I cannot access it and get an error.

External table is not in the expected format

I make the user download the file as

System.Web.HttpResponse response = System.Web.HttpContext.Current.Response;
            // first let's clean up the response.object
            response.Clear();
            response.Charset = "";
            // set the response mime type for excel
            response.ContentType = "application/vnd.ms-excel";
            response.AddHeader("Content-Disposition", "attachment;filename=\"" + filename + "\"");
            // create a string writer
            using (System.IO.StringWriter sw = new System.IO.StringWriter())
            {
                using (System.Web.UI.HtmlTextWriter htw = new System.Web.UI.HtmlTextWriter(sw))
                {
                    // instantiate a datagrid
                    System.Web.UI.WebControls.DataGrid dg = new System.Web.UI.WebControls.DataGrid();
                    dg.DataSource = dt;
                    dg.DataBind();
                    dg.RenderControl(htw);
                    response.Write(sw.ToString());
                    response.End();
                }
            }

The user upload the file after making changes and I am reading it as

string connString = "Provider=Microsoft.Jet.OLEDB.4.0;" +
                "Data Source=" + path + "\\" + FileUpload1.FileName + ";Extended Properties=Excel 8.0;";
                    OleDbConnection oledbConn = new OleDbConnection(connString);

                    oledbConn.Open();

                    OleDbCommand cmd = new OleDbCommand("SELECT * FROM [$Sheet1 ", oledbConn);
                    OleDbDataAdapter oleda = new OleDbDataAdapter();
                    oleda.SelectCommand = cmd;

                    DataSet ds = new DataSet();

                    oleda.Fill(ds, "Employees");

Kindly help. Thanks.