Downloading File From the Grid View

if (e.CommandName == "View")
        {
            ImageButton lb = (ImageButton)e.CommandSource;
            GridViewRow gvr = (GridViewRow)lb.NamingContainer;
            string id = (string)gvdetails.DataKeys[gvr.RowIndex].Value;
            Session["applciationid"] = id;
            DataSet ds = obj.GetDisbursmentDetais(id);
            Session["DocumentLocation"] = ds.Tables[0].Rows[0]["DocuemtnFile"].ToString();
            string filename = Server.MapPath(Session["DocumentLocation"].ToString());
            FileInfo fileInf = new FileInfo(filename);
            if (fileInf.Exists)
            {
                Response.Clear();
                Response.AddHeader("Content-Disposition", "inline;attachment; filename=" + fileInf.Name);
                Response.AddHeader("Content-Length", fileInf.Length.ToString());
                Response.ContentType = "application/octet-stream";
                Response.Flush();
                Response.TransmitFile(fileInf.FullName);
            }
            else
            {
               Label1.Text="<script>"+Environment.NewLine+"alert('NO File is there')</script>";
            }
        }