How to get ELMAH to work with ASP NET MVC HandleError attribute

Question

I am trying to use ELMAH to log errors in my ASP NET MVC application  however when I use the  HandleError  attribute on my controllers ELMAH doesn t log any errors when they occur   As I am guessing its because ELMAH only logs unhandled errors and the  HandleError  attribute is handling the error so thus no need to log it   How do I modify or how would I go about modifying the attribute so ELMAH can know that there was an error and log it    Edit  Let me make sure everyone understands  I know I can modify the attribute thats not the question I m asking    ELMAH gets bypassed when using the handleerror attribute meaning it won t see that there was an error because it was handled already by the attribute    What I am asking is there a way to make ELMAH see the error and log it even though the attribute handled it   I searched around and don t see any methods to call to force it to log the error

User · Answer

This is exactly what I needed for my MVC site configuration!

I added a little modification to the OnException method to handle multiple HandleErrorAttribute instances, as suggested by Atif Aziz:

bear in mind that you may have to take care that if multiple HandleErrorAttribute instances are in effect then duplicate logging does not occur.

I simply check context.ExceptionHandled before invoking the base class, just to know if someone else handled the exception before current handler.
It works for me and I post the code in case someone else needs it and to ask if anyone knows if I overlooked anything.

Hope it is useful:

public override void OnException(ExceptionContext context)
{
    bool exceptionHandledByPreviousHandler = context.ExceptionHandled;

    base.OnException(context);

    Exception e = context.Exception;
    if (exceptionHandledByPreviousHandler
        || !context.ExceptionHandled  // if unhandled, will be logged anyhow
        || RaiseErrorSignal(e)        // prefer signaling, if possible
        || IsFiltered(context))       // filtered?
        return;

    LogException(e);
}

User · Answer

A completely alternative solution is to not use the MVC HandleErrorAttribute  and instead rely on ASP Net error handling  which Elmah is designed to work with   You need to remove the default global HandleErrorAttribute from App Start FilterConfig  or Global asax   and then set up an error page in your Web config    lt customErrors mode  RemoteOnly  defaultRedirect    error     gt    Note  this can be an MVC routed URL  so the above would redirect to the ErrorController Index action when an error occurs

User · Answer

Sorry  but I think the accepted answer is an overkill  All you need to do is this   public class ElmahHandledErrorLoggerFilter   IExceptionFilter       public void OnException  ExceptionContext context                   Log only handled exceptions  because all other will be caught by ELMAH anyway          if  context ExceptionHandled              ErrorSignal FromCurrentContext   Raise context Exception             and then register it  order is important  in Global asax cs   public static void RegisterGlobalFilters  GlobalFilterCollection filters        filters Add new ElmahHandledErrorLoggerFilter         filters Add new HandleErrorAttribute

User · Answer

You can take the code above and go one step further by introducing a custom controller factory that injects the HandleErrorWithElmah attribute into every controller   For more infomation check out my blog series on logging in MVC  The first article covers getting Elmah set up and running for MVC   There is a link to downloadable code at the end of the article  Hope that helps   http   dotnetdarren wordpress com

User · Answer

I m new in ASP NET MVC  I faced the same problem  the following is my workable in my Erorr vbhtml  it work if you only need to log the error using Elmah log    ModelType System Web Mvc HandleErrorInfo       Code         ViewData  Title      Error          Dim item As HandleErrorInfo   CType Model  HandleErrorInfo            To log error with Elmah         Elmah ErrorLog GetDefault HttpContext Current  Log New Elmah Error Model Exception  HttpContext Current       End Code   lt h2 gt      Sorry  an error occurred while processing your request  lt br   gt        item ActionName lt br   gt       item ControllerName lt br   gt       item Exception Message  lt  h2 gt     It is simply

User · Answer

There is now an ELMAH MVC package in NuGet that includes an improved solution by Atif and also a controller that handles the elmah interface within MVC routing  no need to use that axd anymore  The problem with that solution  and with all the ones here  is that one way or another the elmah error handler is actually handling the error  ignoring what you might want to set up as a customError tag or through ErrorHandler or your own error handler The best solution IMHO is to create a filter that will act at the end of all the other filters and log the events that have been handled already  The elmah module should take care of loging the other errors that are unhandled by the application  This will also allow you to use the health monitor and all the other modules that can be added to asp net to look at error events  I wrote this looking with reflector at the ErrorHandler inside elmah mvc  public class ElmahMVCErrorFilter   IExceptionFilter      private static ErrorFilterConfiguration  config      public void OnException ExceptionContext context              if  context ExceptionHandled    The unhandled ones will be picked by the elmah module                     var e   context Exception             var context2   context HttpContext ApplicationInstance Context               TODO  Add additional variables to context HttpContext Request ServerVariables for both handled and unhandled exceptions            if   context2    null        RaiseErrorSignal e  context2   amp  amp    IsFiltered e  context2                              LogException e  context2                                  private static bool  IsFiltered System Exception e  System Web HttpContext context              if   config    null                       config    context GetSection  elmah errorFilter   as ErrorFilterConfiguration     new ErrorFilterConfiguration                    var context2   new ErrorFilterModule AssertionHelperContext  System Exception e  context          return  config Assertion Test context2            private static void  LogException System Exception e  System Web HttpContext context              ErrorLog GetDefault  System Web HttpContext context  Log new Elmah Error  System Exception e   System Web HttpContext context              private static bool  RaiseErrorSignal System Exception e  System Web HttpContext context              var signal   ErrorSignal FromContext  System Web HttpContext context          if  signal    null                      return false                  signal Raise  System Exception e   System Web HttpContext context          return true           Now  in your filter config you want to do something like this       public static void RegisterGlobalFilters GlobalFilterCollection filters                  These filters should go at the end of the pipeline  add all error handlers before         filters Add new ElmahMVCErrorFilter             Notice that I left a comment there to remind people that if they want to add a global filter that will actually handle the exception it should go BEFORE this last filter  otherwise you run into the case where the unhandled exception will be ignored by the ElmahMVCErrorFilter because it hasn t been handled and it should be loged by the Elmah module but then the next filter marks the exception as handled and the module ignores it  resulting on the exception never making it into elmah   Now  make sure the appsettings for elmah in your webconfig look something like this    lt add key  elmah mvc disableHandler  value  false    gt   lt  -- This handles elmah controller pages  if disabled elmah pages will not work -- gt   lt add key  elmah mvc disableHandleErrorFilter  value  true    gt   lt  -- This uses the default filter for elmah  set to disabled to use our own -- gt   lt add key  elmah mvc requiresAuthentication  value  false    gt   lt  -- Manages authentication for elmah pages -- gt   lt add key  elmah mvc allowedRoles  value       gt   lt  -- Manages authentication for elmah pages -- gt   lt add key  elmah mvc route  value  errortracking    gt   lt  -- Base route for elmah pages -- gt    The important one here is  elmah mvc disableHandleErrorFilter   if this is false it will use the handler inside elmah mvc that will actually handle the exception by using the default HandleErrorHandler that will ignore your customError settings  This setup allows you to set your own ErrorHandler tags in classes and views  while still loging those errors through the ElmahMVCErrorFilter  adding a customError configuration to your web config through the elmah module  even writing your own Error Handlers  The only thing you need to do is remember to not add any filters that will actually handle the error before the elmah filter we ve written  And I forgot to mention  no duplicates in elmah

User · Answer

You can subclass HandleErrorAttribute and override its OnException member  no need to copy  so that it logs the exception with ELMAH and only if the base implementation handles it  The minimal amount of code you need is as follows   using System Web Mvc  using Elmah   public class HandleErrorAttribute   System Web Mvc HandleErrorAttribute       public override void OnException ExceptionContext context                base OnException context           if   context ExceptionHandled               return          var httpContext   context HttpContext ApplicationInstance Context          var signal   ErrorSignal FromContext httpContext           signal Raise context Exception  httpContext             The base implementation is invoked first  giving it a chance to mark the exception as being handled  Only then is the exception signaled  The above code is simple and may cause issues if used in an environment where the HttpContext may not be available  such as testing  As a result  you will want code that is that is more defensive  at the cost of being slightly longer    using System Web  using System Web Mvc  using Elmah   public class HandleErrorAttribute   System Web Mvc HandleErrorAttribute       public override void OnException ExceptionContext context                base OnException context           if   context ExceptionHandled          if unhandled  will be logged anyhow                TryRaiseErrorSignal context     prefer signaling  if possible                IsFiltered context              filtered              return           LogException context              private static bool TryRaiseErrorSignal ExceptionContext context                var httpContext   GetHttpContextImpl context HttpContext           if  httpContext    null              return false          var signal   ErrorSignal FromContext httpContext           if  signal    null              return false          signal Raise context Exception  httpContext           return true             private static bool IsFiltered ExceptionContext context                var config   context HttpContext GetSection  elmah errorFilter                           as ErrorFilterConfiguration           if  config    null              return false           var testContext   new ErrorFilterModule AssertionHelperContext                                context Exception                                 GetHttpContextImpl context HttpContext            return config Assertion Test testContext              private static void LogException ExceptionContext context                var httpContext   GetHttpContextImpl context HttpContext           var error   new Error context Exception  httpContext           ErrorLog GetDefault httpContext  Log error              private static HttpContext GetHttpContextImpl HttpContextBase context                return context ApplicationInstance Context            This second version will try to use error signaling from ELMAH first  which involves the fully configured pipeline like logging  mailing  filtering and what have you  Failing that  it attempts to see whether the error should be filtered  If not  the error is simply logged  This implementation does not handle mail notifications  If the exception can be signaled then a mail will be sent if configured to do so   You may also have to take care that if multiple HandleErrorAttribute instances are in effect then duplicate logging does not occur  but the above two examples should get your started

User · Answer

For me it was very important to get email logging working  After some time I discover that this need only 2 lines of code more in Atif example   public class HandleErrorWithElmahAttribute   HandleErrorAttribute       static ElmahMVCMailModule error mail log   new ElmahMVCMailModule         public override void OnException ExceptionContext context                error mail log Init HttpContext Current ApplicationInstance                                     I hope this will help someone

[asp.net-mvc] How to get ELMAH to work with ASP.NET MVC [HandleError] attribute?

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