全局log4net

 public class FilterConfig
    {
        public static void RegisterGlobalFilters(GlobalFilterCollection filters)
        {
            filters.Add(new SysExceptionAttribute());
        }
    }
    public class SysExceptionAttribute : HandleErrorAttribute
    {
        protected ILog log = LogManager.GetLogger(typeof(SysExceptionAttribute));

        public override void OnException(ExceptionContext filterContext)
        {
            string controller = filterContext.RouteData.Values["controller"].ToString();
            string action = filterContext.RouteData.Values["action"].ToString();
            string msg = filterContext.Exception.Message;
            string stackTrace = filterContext.Exception.StackTrace;
            string clientIP = Common.UntilHelper.GetClientIp();
            log.Error("Ajax：" + filterContext.HttpContext.Request.IsAjaxRequest() + "；IP地址：" + clientIP + "；访问路由：" + controller + "/" + action + "；URL：" + filterContext.HttpContext.Request.RawUrl + "；Message：" + msg + "；StackTrace：" + stackTrace);

            if (filterContext.HttpContext.Request.IsAjaxRequest())
            {
                filterContext.HttpContext.Response.Write("error");
            }
            else
            {
                filterContext.HttpContext.Response.Redirect("/common/error");
            }
            filterContext.HttpContext.Response.End();
        }

    }

在Global.asax中加入：

     protected void Application_Start()
        {
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        }

也可以写到

protected void Application_Error(object sender, EventArgs e){}