Document download by document path under Extaspnet

<ext:button id= "Button1" runat= "Server" text= "button" onclick= "Button1_Click" enableajax= "false" >//<span Style= "Font-family:arial, Helvetica, Sans-serif;" >enableajax= "False" is the most important </span>        </ext:Button>

protected void Button1_Click (object sender, EventArgs e)    {        try        {            string filepath = "E:\\123.xls";            string filename = System.IO.Path.GetFileName (filepath);            Response.Clear ();            Response.ClearHeaders ();            Response.Buffer = false;            Response.ContentType = "Application/octet-stream";            Response.contentencoding=system.text.encoding.getencoding ("Utf-8");            Response.AddHeader ("Content-disposition", "attachment; Filename= "+ System.Web.HttpUtility.UrlEncode (filename, Encoding.UTF8));            Response.WriteFile (filepath);            Response.Flush ();            Response.End ();        }        catch (Exception E)        {            //alert ("The data you want to download is not found!
");        }    }

Document download by document path under Extaspnet