在一个网站的开发测试阶段，我们经常需要全局捕获异常。使得网站在异常发生时并不会整个崩掉，从而影响到所有用户的访问，同时记录下异常的详细信息，以便于网站维护人员在异常发生后，可以准确定位异常所在位置和原因。本文使用过滤器的方式来实现全局异常捕获。网上也有很多类似的博文教程，我这里整理了一份日志打印比较完整的。

新建过滤器

在您的Util项目添加过滤器ExceptionLogAttribute.cs：

using System;

using System.Web;

using System.Web.Mvc;

using YourNameSpace.Util.Helpper;

using NLog;



namespace YourNameSpace.Util.Extensions

{

    [AttributeUsage(AttributeTargets.Class, Inherited = true, AllowMultiple = false)]

    public class ExceptionLogAttribute : HandleErrorAttribute

    {

        public override void OnException(ExceptionContext filterContext)

        {

            if (!filterContext.ExceptionHandled)

            {

                Logger logger = LogManager.GetCurrentClassLogger();

                try

                {

                    var controllerName = (string)filterContext.RouteData.Values["controller"];

                    var actionName = (string)filterContext.RouteData.Values["action"];

                    var memberId = filterContext.Controller.ViewBag.MemberId;

                    var exception = filterContext.Exception;

                    if (filterContext.HttpContext != null && filterContext.HttpContext.Request != null)

                    {

                        if (filterContext.HttpContext.Request.RequestType == "GET")

                        {

                            var requestUrl = filterContext.HttpContext.Request.Url.ToString();

                            var requestParas = filterContext.HttpContext.Request.Params;

                            if (requestParas != null)

                            {

                                var reqParaStr = HttpUtility.UrlDecode(requestParas.ToString());

                                logger.Error(LoggerHelper.GetErrorMsg(exception, controllerName, actionName, memberId, requestUrl, reqParaStr));

                            }

                            else

                            {

                                logger.Error(LoggerHelper.GetErrorMsg(exception, controllerName, actionName, memberId, requestUrl));

                            }

                        }

                        else if (filterContext.HttpContext.Request.RequestType == "POST")

                        {

                            var requestUrl = filterContext.HttpContext.Request.Url.ToString();

                            var requestParas = filterContext.HttpContext.Request.Params;

                            if (requestParas != null)

                            {

                                var reqParaStr = HttpUtility.UrlDecode(requestParas.ToString());

                                logger.Error(LoggerHelper.GetErrorMsg(exception, controllerName, actionName, memberId, requestUrl, reqParaStr));

                            }

                            else

                            {

                                logger.Error(LoggerHelper.GetErrorMsg(exception, controllerName, actionName, memberId, requestUrl));

                            }

                        }

                        else

                        {

                            logger.Error(LoggerHelper.GetErrorMsg(exception, controllerName, actionName, memberId));

                        }

                    }

                    else

                    {

                        logger.Error(LoggerHelper.GetErrorMsg(exception, controllerName, actionName, memberId));

                    }

                }

                catch (Exception e)

                {

                    logger.Error(LoggerHelper.GetErrorMsg(e, "ExceptionLogAttribute", "异常过滤器", "未知"));

                }

            }

            filterContext.ExceptionHandled = true;

        }

    }

}

关于NLog的配置和使用，本文不再赘述。可自行百度进行配置。

在您的Util项目中添加日志帮助类LoggerHelper.cs:

using System;using System.Text;namespace YourNameSpace.Util.Helpper{    public class LoggerHelper    {        public static string GetErrorMsg(Exception exception, string controllerName, string actionName, Guid memberId, string requestUrl = null, string requestParams = null, string extraMsg = null)        {            return GetErrorMsg(exception, controllerName, actionName, memberId.ToString(), requestUrl, requestParams, extraMsg);        }        /// 
        /// 获取接口异常详细信息函数        /// 
        /// 异常对象        /// 控制器名称
///
接口名称
/param>        ///
param name="memberId">用户Id
        /// 请求URL        /// 请求参数        /// 需要额外打印输出的日志信息        ///         public static string GetErrorMsg(Exception exception, string controllerName, string actionName, string memberId, string requestUrl = null, string requestParams = null, string extraMsg = null)        {            var erroMsg = new StringBuilder();            if (!string.IsNullOrWhiteSpace(extraMsg))            {                erroMsg.Append(extraMsg);            }            erroMsg.Append($"控制器：{controllerName}/{actionName} \n") ;            if(string.IsNullOrWhiteSpace(memberId))            {                erroMsg.Append($"无用户Id \n ");            }            else            {                erroMsg.Append($"用户Id：{memberId} \n ");            }            erroMsg.Append($"ExceptionMessage:{exception.Message} \n InnerException:{exception.InnerException} \n StackTrace:{exception.StackTrace} \n");            if (!string.IsNullOrWhiteSpace(requestUrl))            {                erroMsg.Append($"Request.Url:{requestUrl} \n");            }            if (!string.IsNullOrWhiteSpace(requestParams))            {                erroMsg.Append($"Request.Params:{requestParams} \n");            }            return erroMsg.ToString();        }    }}

注册全局过滤器

在【您的web项目】->【App_Start】->【FilterConfig.cs】中引用过滤器，并注册全局异常捕获过滤器。

using System.Web.Mvc;using YourNameSpace.Util.Filters;using YourNameSpace.Util.Extensions;namespace YourNameSpace.Web{    public class FilterConfig    {        public static void RegisterGlobalFilters(GlobalFilterCollection filters)        {            //注册全局过滤器            filters.Add(new HandleErrorAttribute());            //注册全局异常捕获过滤器            filters.Add(new ExceptionLogAttribute());        }    }}

全局异常日志打印结果