export gridview to excel

See more:

ASP.NET4

I am exporting a gridview(dynamically created) data to excel.In my local machine it is downloaded.But if I drag the row to increase or drag the column and close the file it wants me to save as usual.I save the changes.Now, after a second a folder is being created automatically with html files and css. If I delete the folder the excel file can not be opened.It requires an html file which was in that folder.The folder is not created when I download the file.Only if I change any thing in that file the folder is created.

my code----------------------------------------------

private void ExportToExcel(DataTable dt)
{
if (dt.Rows.Count > 0)
{
string filename = "Downloaded" + DateTime.Now.ToString("ddMMyyss") + ".xls";
System.IO.StringWriter tw = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter hw = new System.Web.UI.HtmlTextWriter(tw);
DataGrid dgGrid = new DataGrid();
dgGrid.DataSource = dt;
dgGrid.DataBind();
dgGrid.ItemStyle.VerticalAlign = VerticalAlign.Top;
//Get the HTML for the control.
dgGrid.RenderControl(hw);
//Write the HTML back to the browser.
//Response.ContentType = application/vnd.ms-excel;
Response.ClearContent();
Response.ContentType = "application/vnd.ms-excel";
Response.AppendHeader("Content-Disposition", "attachment; filename=" + filename + "");
this.EnableViewState = false;

string brstyle = @"<style>br { mso-data-placement:same-cell; }</style>"; //--as i have to create two lines in a cell--//
Response.Write(brstyle);
Response.Write(tw.ToString());
Response.Flush();
Response.End();
}
}