Can't read excel file after creating it using File.WriteAllText() function

Question

Hi all,

I have created an excel sheet from datatable using function. I want to read the excel sheet programatically using the below connectionstring. This string works fine for all other excel sheets but not for the one i created using the function. I guess it is because of excel version problem.

   OleDbConnection conn= new OleDbConnection("Data Source='" + path +"';provider=Microsoft.Jet.OLEDB.4.0;Extended Properties=Excel 8.0;";);  

Can anyone suggest a way by which i can create an excel sheet such that it is readable again using above query. I cannot use Microsoft InterOp library as it is not supported by my host. I have even changed different encoding formats. Still it doesnt work

 public void ExportDataSetToExcel(DataTable dt)
{
    HttpResponse response = HttpContext.Current.Response;        
    response.Clear();
    response.Charset = "utf-8";
    response.ContentEncoding = Encoding.GetEncoding("utf-8"); 
    response.ContentType = "application/vnd.ms-excel";
    Random Rand = new Random(); int iNum = Rand.Next(10000, 99999);
    string extension = ".xls";
    string filenamepath = AppDomain.CurrentDomain.BaseDirectory + "graphs\\" + iNum + ".xls";        
    string file_path = "graphs/" + iNum + extension;

    response.AddHeader("Content-Disposition", "attachment;filename=\"" + iNum + "\"");
    string query = "insert into graphtable(graphtitle,graphpath,creategraph,year) VALUES('" + iNum.ToString() + "','" + file_path + "','" + true + "','" + DateTime.Now.Year.ToString() + "')";
    try
    {
        int n = connect.UpdateDb(query);
        if (n > 0)
        {
            resultLabel.Text = "Merge Successfull";
        }
        else
        {
            resultLabel.Text = " Merge Failed";
        }
        resultLabel.Visible = true;
    }
    catch { }    
    using (StringWriter sw = new StringWriter())
    {
        using (HtmlTextWriter htw = new HtmlTextWriter(sw))
        {
            // instantiate a datagrid
            DataGrid dg = new DataGrid();
            dg.DataSource = dt; //ds.Tables[0];
            dg.DataBind();                
            dg.RenderControl(htw);
            File.WriteAllText(filenamepath, sw.ToString());    // File.WriteAllText(filenamepath, sw.ToString(), Encoding.UTF8);
            response.Write(sw.ToString());
            response.End();
        }
    }
}

Answer 1

You seem to be writing a dataset as HtmlText and then trying to tell it that it's an Excel file. Unless it's something I'm missing that's unlikely to work since Excel files are a specific format and so needs to be written in that format. If you take the file you've created and tries to open it in Excel, what happens?

One way around it would be to write your data as a CSV file which can be read both with Excel or with an OleDBConnection.