Neither the Global Exception Filter or the Application_Error are Catching Unhandled Exceptions

Question

I have a global exception filter named LogErrorAttribute:

public class LogErrorAttribute : IExceptionFilter
{
    private ILogUtils logUtils;

    public void OnException(ExceptionContext filterContext)
    {
        if (this.logUtils == null)
        {
            this.logUtils = StructureMapConfig.Container.GetInstance<ILogUtils>();
        }

        this.logUtils.LogError(HttpContext.Current.User.Identity.GetUserId(), "Unknown error.", filterContext.Exception);
    }
}

It's registered along with the standard HandleErrorAttribute filter:

filters.Add(new LogErrorAttribute());
filters.Add(new HandleErrorAttribute());

I'm registering those filters like this:

FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);

I also have an Application_Error fallback:

protected void Application_Error()
{
    var exception = Server.GetLastError();
    Server.ClearError();
    var httpException = exception as HttpException;

    //Logging goes here

    var routeData = new RouteData();
    routeData.Values["controller"] = "Error";
    routeData.Values["action"] = "Index";

    if (httpException != null)
    {
        if (httpException.GetHttpCode() == 404)
        {
            routeData.Values["action"] = "NotFound";
        }
        Response.StatusCode = httpException.GetHttpCode();
    }
    else
    {
        Response.StatusCode = 500;
    }

    // Avoid IIS7 getting involved
    Response.TrySkipIisCustomErrors = true;

    // Execute the error controller
    if (exception != null)
    {
        this.errorLogger.Log(LogLevel.Error, "An unknown exception has occurred.", exception);
    }
    else if (httpException != null)
    {
        this.errorLogger.Log(LogLevel.Error, "An unknown HTTP exception has occurred.", httpException);
    }
    else
    {
        this.errorLogger.Log(LogLevel.Error, "An unknown error has occurred.");
    }
}

Now, I have an API controller that grabs some data from the database and then uses AutoMapper to map the models to view models:

var viewModels = AutoMapper.Mapper.Map(users, new List<UserViewModel>());

Inside that AutoMapper configuration a custom resolver executes for one of the properties:

var appModuleAssignments = this.appModuleAssignmentManager.Get(userId);
var appModules = appModuleAssignments.Select(x => this.appModuleManager.Get(x.AppModuleId));
return AutoMapper.Mapper.Map(appModules, new List<AppModuleViewModel>());

At the moment I'm forcing the appModuleManager.Get statement to throw a regular exception:

throw new Exception("Testing global filter.");

This subsequently throws an exception in AutoMapper, both of which are unhandled, however neither the global filter or the Application_Error are picking up this exception.

What did I do wrong here?

---

A couple things I have done since posting:

1. Added the customErrors attribute to the Web.config to turn them on.
2. Removed the HandleErrorAttribute global filter because I realized it was setting the error to handled if it were even running. I would not expect it to be executing anyway because this error occurs outside the controller, but it would have likely bit me later.

Answer 1

The short answer is that you are adding a MVC Exception Filter rather than a Web API Exception Filter.

Your implementation checks for ExceptionContext rather than HttpActionExecutedContext

public override void OnException(HttpActionExecutedContext actionExecutedContext)

Since the framework will raises a Http Exception rather than a MVC Exception, your OnException override method is not triggered.

So, a more complete example:

public class CustomExceptionFilter : ExceptionFilterAttribute

    {
       public override void OnException(HttpActionExecutedContext actionExecutedContext)

      {

        message = "Web API Error";
        status = HttpStatusCode.InternalServerError;

        actionExecutedContext.Response = new HttpResponseMessage()
        {
            Content = new StringContent(message, System.Text.Encoding.UTF8, "text/plain"),
            StatusCode = status
        };

        base.OnException(actionExecutedContext);
    }
}

Another important step is to register your Global Web API Exception Filter in WebApiConfig.cs, in the Register(HttpConfiguration config) method.

public static void Register(HttpConfiguration config)
{

...

config.Filters.Add(new CustomExceptionFilter());

}