MVC四大筛选器—ExceptionFilter

该筛选器是在系统出现异常时触发，可以对抛出的异常进行处理。所有的ExceptionFilter筛选器都是实现自IExceptionFilter接口  

    public interface IExceptionFilter

    {

        void OnException(ExceptionContext filterContext);

    }

实现OnException方法来实现对异常的自定义处理

MVC4中实现了默认的异常处理机制，源码如下 

public virtual void OnException(ExceptionContext filterContext)

        {

            if (filterContext == null)

            {

                throw new ArgumentNullException("filterContext");

            }

            if (filterContext.IsChildAction)

            {

                return;

            }



            // If custom errors are disabled, we need to let the normal ASP.NET exception handler

            // execute so that the user can see useful debugging information.

            if (filterContext.ExceptionHandled || !filterContext.HttpContext.IsCustomErrorEnabled)

            {

                return;

            }



            Exception exception = filterContext.Exception;



            // If this is not an HTTP 500 (for example, if somebody throws an HTTP 404 from an action method),

            // ignore it.

            if (new HttpException(null, exception).GetHttpCode() != 500)

            {

                return;

            }



            if (!ExceptionType.IsInstanceOfType(exception))

            {

                return;

            }



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

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

            HandleErrorInfo model = new HandleErrorInfo(filterContext.Exception, controllerName, actionName);

            filterContext.Result = new ViewResult

            {

                ViewName = View,

                MasterName = Master,

                ViewData = new ViewDataDictionary<HandleErrorInfo>(model),

                TempData = filterContext.Controller.TempData

            };

            filterContext.ExceptionHandled = true;

            filterContext.HttpContext.Response.Clear();

            filterContext.HttpContext.Response.StatusCode = 500;



            // Certain versions of IIS will sometimes use their own error page when

            // they detect a server error. Setting this property indicates that we

            // want it to try to render ASP.NET MVC's error page instead.

            filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;

        }

Application_Start中将HandleErrorAttribute添加到全局筛选器GlobalFilterCollection中，系统即会对异常进行对应的处理。

我们现在实现一个自定义的异常处理筛选器，在处理完后记录异常信息至日志文件中  

 public class MyExceptionHandleAttribute : HandleErrorAttribute

    {

        public MyExceptionHandleAttribute()

            : base()

        {

        }



        public void OnException(ExceptionContext filterContext)

        {

            base.OnException(filterContext);

            //记录日志

            log.Info(filterContext.Exception);

        }

    }

在GlobalFilterCollection添加MyExceptionHandleAttribute 即可使用自定义的异常筛选器来处理