Export and Import Excel to Sql Database

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C#

good morning everybody,

i am exporting the data from Sql table....my code is given below
actually i am using same Excel Sheet ...first of all i export Excel sheet then same sheet i am trying to import in samr Sql table...

private void ExportToExcel(string strFileName, DataGrid dg)
    {
        Response.ClearContent();
        Response.AddHeader("content-disposition", "attachment; filename=" + strFileName);
        Response.ContentType = "application/excel";
        System.IO.StringWriter sw = new System.IO.StringWriter();
        HtmlTextWriter htw = new HtmlTextWriter(sw);
        dg.RenderControl(htw);
        Response.Write(sw.ToString());
        Response.End();
    }

    protected void Button1_Click1(object sender, EventArgs e)
    {
       
        SqlDataAdapter ad = new SqlDataAdapter("select * from st", strConnection1);
        strConnection1.Open();

        DataTable dtOriginal = new DataTable();
        ad.Fill(dtOriginal );
    
        //Create Tempory Table
        DataTable dtTemp = new DataTable();

        //Creating Header Row
        dtTemp.Columns.Add(" Name");
        dtTemp.Columns.Add("Age");
      
       

        DataRow drAddItem;
        for (int i = 0; i < dtOriginal.Rows.Count; i++)
        {
            drAddItem = dtTemp.NewRow();
            drAddItem[0] = dtOriginal.Rows[i][0].ToString();//Name
            drAddItem[1] = dtOriginal.Rows[i][1].ToString();//Age

           

            dtTemp.Rows.Add(drAddItem);
        }

        //Temp Grid
       
        DataGrid dg = new DataGrid();
        dg.DataSource = dtTemp;
        dg.DataBind();
        ExportToExcel("Sheet1.xls", dg);
        dg = null;
        dg.Dispose();
        strConnection1.Close();
    }

so is generate the excel sheet on my drive with name Sheet1.xls

then i try to import this data again into Sql Table.
then i give an error-"External table is not in the expected format."

if i self create a sheet1.xls with same schema then it work and import data in to table.
my code is--

on button click-
{
  string excelConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=H:\Sheet1.xls;Extended Properties=""Excel 12.0 Xml;HDR=YES""";
      
      
      //Create Connection to Excel work book
         
        OleDbConnection excelConnection =new OleDbConnection(excelConnectionString);
         //Create OleDbCommand to fetch data from Excel
        /*   OleDbCommand cmd = new OleDbCommand("Select [ID],[Name],[Designation] from [Sheet1$]", excelConnection);
          excelConnection.Open();
          OleDbDataReader dReader;
          dReader = cmd.ExecuteReader();
          SqlBulkCopy sqlBulk = new SqlBulkCopy(strConnection);
          //Give your Destination table name
          sqlBulk.DestinationTableName = "Excel_table";
          sqlBulk.WriteToServer(dReader);
          excelConnection.Close(); */
        ////////////////////
       
         OleDbCommand cmd1 = new OleDbCommand("Select * from [Sheet1$]", excelConnection);
         excelConnection.Open();
         OleDbDataReader dReader2;
         dReader2 = cmd1.ExecuteReader();
         SqlBulkCopy sqlBulk1 = new SqlBulkCopy(strConnection);
         //Give your Destination table name
         sqlBulk1.DestinationTableName = "st";
         sqlBulk1.WriteToServer(dReader2);
         excelConnection.Close(); 
      }

so please help me so that i can export and import same Excel sheet.
thanks