protected void Export_to_Excel(object sender, EventArgs e)
{
Response.Clear();
Response.AddHeader("content-disposition", "attachment;filename=PatientSearchReport.xls");
Response.ContentType = "application/vnd.xlsx";
System.IO.StringWriter stringWrite = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
GridView1.RenderControl(htmlWrite);
string html2 = Regex.Replace(stringWrite.ToString(), @"(<input type=""image""\/?[^>]+>)", @"", RegexOptions.IgnoreCase);
html2 = Regex.Replace(html2, @"(<input type=""checkbox""\/?[^>]+>)", @"", RegexOptions.IgnoreCase);
html2 = Regex.Replace(html2, @"(]+>)", @"", RegexOptions.IgnoreCase);
Response.Write(html2.ToString());
Response.End();
}