asp.net 在global中拦截404错误

  

  void Application_Error(object sender, EventArgs e)
    {
        if(Context != null)
        {
            HttpContext ctx   =   HttpContext.Current;
            Exception ex   =   ctx.Server.GetLastError();
            HttpException ev   =   ex as HttpException;
            if(ev!= null)
            {
                if(ev.GetHttpCode()   ==   404)
                {
                    ctx.ClearError();
                    Response.Redirect("~/nofound.aspx", false);
                    Response.End();
                }
                else
                {
                    Server.Transfer("~/Error.aspx", false);
                }
            }
        }
    }