dissable multiple enter key press

protected void Page_Load(object sender, EventArgs e)
   {

       if (!IsPostBack)
       {
           Session["CheckRefresh"] = Server.UrlDecode(System.DateTime.Now.ToString());
       }
   }
 protected void Page_PreRender(object sender, EventArgs e)
   {
       ViewState["CheckRefresh"] = Session["CheckRefresh"];
   }

 protected void SubmitClick(object sender, EventArgs e)
 {
     try
     {
         if (Session["CheckRefresh"].ToString() == ViewState["CheckRefresh"].ToString())
         {
            

             //Your Code For Submit Or Update
 Session["CheckRefresh"] = Server.UrlDecode(System.DateTime.Now.ToString());

         }
     }
     catch (Exception ex)
     {
         throw (ex);
     }
 }