private void DownloadFile(string fname)
    {
        string myPath = Path.GetFullPath(fname);
        string name = Path.GetFileName(myPath);
        string ext = Path.GetExtension(myPath);
        string type = "";
        // set known types based on file extension  
        if (ext != null)
        {
            switch (ext.ToLower())
            {
                case ".htm":
                case ".html":
                    type = "text/HTML";
                    break;
 
                case ".txt":
                    type = "text/plain";
                    break;
 
                case ".doc":
                case ".rtf":
                    type = "Application/msword";
                    break;
 
                case ".xls":
                    type = "Application/excel";
                    break;
 
                default:
                    type = "text/plain";
                    break;
            }
        }
            Response.Buffer = true;
            Response.AppendHeader("content-disposition", "attachment; filename=" + name);
            //Response.AppendHeader("Pragma","cache");
            //Response.AppendHeader("Expires", "-1");
            if (type != "")
                Response.ContentType = type;
 
            Response.WriteFile(myPath);
            Response.End();
    }