Export to excell file

Question

i want to create a function that would export an excell file according to a dynamically created table in web page..as in same format..please help me

 

please see my snippet:

 

GridView1.AllowPaging = true;

StringWriter tw = new StringWriter();
System.Web.UI.HtmlTextWriter hw = new System.Web.UI.HtmlTextWriter(tw);

HtmlForm frm = new HtmlForm();
string strTmpTime = (System.DateTime.Today).ToString();

if (strTmpTime.IndexOf("/") != -1)
{
   strTmpTime = strTmpTime.Replace("/", "-").ToString().Trim();
}
if (strTmpTime.IndexOf(":") != -1)
{
   strTmpTime = strTmpTime.Replace(":", "-").ToString().Trim();
}
Response.ContentType = "application/ms-excel";
Response.AddHeader("content-disposition", "attachment;filename=sheet.xls");
Response.Charset = "UTF-8";
EnableViewState = false;
Controls.Add(frm);
frm.Controls.Add(GridView1);
frm.RenderControl(hw);
Response.Write(tw.ToString());
Response.End();

 

 

this code gives an error upon opening the excel file:

 

"The file you are trying to open, [filename], is in a different format than specified by the file extension" error opening Excel files