[Bug] exception not catched into the modal component

[adrienbarde]

Describe the bug

I use a ilogger global exception handler and I call services from my component which is in my modal.
when a service throws an exception I can't catch it from my global handler.

it works fine all the application except for the exceptions of the services called by my component in the modal

Is there a way to catch the exception that thrown inside the modal? Is it a different thread? A cascading problem?

** Code **

My Ilogger

    public interface IUnhandledExceptionSender
    {
        event EventHandler<Exception> UnhandledExceptionThrown;
    }

    public class UnhandledExceptionSender : ILogger, IUnhandledExceptionSender
    {

        public event EventHandler<Exception> UnhandledExceptionThrown;

        public IDisposable BeginScope<TState>(TState state)
        {
            return null;
        }

        public bool IsEnabled(LogLevel logLevel)
        {
            return true;
        }

        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state,
            Exception exception, Func<TState, Exception, string> formatter)
        {
            if (exception != null)
            {
                UnhandledExceptionThrown?.Invoke(this, exception);
            }
        }
    }

    public class UnhandledExceptionProvider : ILoggerProvider
    {
        UnhandledExceptionSender _unhandledExceptionSender;
        private ITechnicalLogger _technicalLogger;
        private IToastService _toastService;

        public UnhandledExceptionProvider(UnhandledExceptionSender unhandledExceptionSender, ITechnicalLogger technicalLogger, IToastService toastService)
        {
            _unhandledExceptionSender = unhandledExceptionSender;
            _technicalLogger = technicalLogger;
            _toastService = toastService;
        }

        public ILogger CreateLogger(string categoryName)
        {
            return new UnhandledExceptionLogger(categoryName, _unhandledExceptionSender, _technicalLogger, _toastService);
        }

        public void Dispose()
        {
        }

        public class UnhandledExceptionLogger : ILogger
        {
            private readonly string _categoryName;
            private readonly UnhandledExceptionSender _unhandeledExceptionSender;
            private ITechnicalLogger _technicalLogger;
            private IToastService _toastService;

            public UnhandledExceptionLogger(string categoryName, UnhandledExceptionSender unhandledExceptionSender, ITechnicalLogger technicalLogger, IToastService toastService)
            {
                _unhandeledExceptionSender = unhandledExceptionSender;
                _categoryName = categoryName;
                _technicalLogger = technicalLogger;
                _toastService = toastService;
            }

            public bool IsEnabled(LogLevel logLevel)
            {
                return true;
            }

            public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
            {
                if (exception != null)
                {
                   //All exceptions catched here except from my modal component
                    _technicalLogger.Error("Error occurred", exception);
                }
            }

            public IDisposable BeginScope<TState>(TState state)
            {
                return new NoopDisposable();
            }

            private class NoopDisposable : IDisposable
            {
                public void Dispose()
                {
                }
            }
}

Program init

var unhandledExceptionSender = new UnhandledExceptionSender();
            var unhandledExceptionProvider = new UnhandledExceptionProvider(unhandledExceptionSender, technicalLogger, null);
            builder.Logging.AddProvider(unhandledExceptionProvider);
            builder.Services.AddSingleton<IUnhandledExceptionSender>(unhandledExceptionSender);

App.razor

<CascadingBlazoredModal>
    <Router AppAssembly="typeof(Program).Assembly">
        <Found Context="routeData">
            <RouteView RouteData="routeData" DefaultLayout="typeof(MainLayout)" />
        </Found>
        <NotFound>
            <LayoutView Layout="@typeof(MainLayout)">
                <p>Sorry, there's nothing at this address.</p>
            </LayoutView>
        </NotFound>
    </Router>
</CascadingBlazoredModal>

Method to open the modal

public async Task Edit(int id)
        {
            var parameters = new ModalParameters();
            parameters.Add(nameof(AgencyEdit.AgencyId), id);
            var editModal = Modal.Show<AgencyEdit>("Edit", parameters, new ModalOptions
            {
                Animation = ModalAnimation.FadeIn(1)
            });

            var result = await editModal.Result;
            if (!result.Cancelled)
            {
                await RefreshList();
            }
        }

My Edit component into the modal

public partial class AgencyEdit : ComponentBase
{
        [Inject]
        private IAgencyService _agencyService { get; set; }

        [Inject]
        private IToastService _toastService { get; set; }

        [CascadingParameter] BlazoredModalInstance BlazoredModal { get; set; }

        [Parameter]
        public int AgencyId { get; set; }

        public AgencyViewModel Agency { get; set; }

        protected override async Task OnInitializedAsync()
        {
            await base.OnInitializedAsync();
            Agency = new AgencyViewModel();
        }

        protected override async Task OnParametersSetAsync()
        {
            if (AgencyId > 0)
            {
                Agency = await _agencyService.GetAgency(AgencyId);
            }
        }

        public async void HandleValidSubmit()
        {
              // This method throws an exception !
                await _agencyService.AddAgency(Agency))
        }
}

[chrissainty]

I can't think of how the modal is blocking you getting exceptions in your handler. We don't have any try.. catch blocks in our code which could swallow the exception and threads are not an issue as there is only one thread in the browser.

I've not done any work with logging in Blazor so I'm not familiar with the patterns or any pitfalls/shortcomings. This is something I will be looking into but I'm afraid I don't have the capacity to do it right now.

@larsk2009 do you have any ideas on this one?

[larsk2009]

Not really. I don't have much experience with this either. I guess the easiest way to see the issue is if we have an actual project which shows this issue. Then we can debug that project and probably find what is going on?

[adrienbarde]

Not really. I don't have much experience with this either. I guess the easiest way to see the issue is if we have an actual project which shows this issue. Then we can debug that project and probably find what is going on?

Thank you, here an example of my project => https://github.com/adrienbarde/UnhandledExceptionWithBlazoredModal

where the exception must be caught
Line 72 File => Common\UnhandledExceptionSender.cs

Into this file, there are two examples
=> \Services\AgencyService.cs
1- method "DeleteAgency" is called directly from the page
2- method "UpdateAgency" is called from the modal component

both throw exceptions

the exception coming from "DeleteAgency" is caught
the exception coming from "UpdateAgency" is NOT caught

** how to test **
1- Add a break point Line 72 File => Common\UnhandledExceptionSender.cs
2- launch the project
3- click on Agency menu link
4- click on a "Delete" button to try "DeleteAgency" method
5- Click on "Details" button then click on on "Save" to try the "UpdateAgency"

[larsk2009]

Hi @adrienbarde

I can reproduce your issue with that project. I don't immediately see the issue, but have you had a look at this. It seems logging/exception handling/catching in Blazor is not very mature yet, so maybe something is just going wrong there?

[adrienbarde]

Hi @adrienbarde

I can reproduce your issue with that project. I don't immediately see the issue, but have you had a look at this. It seems logging/exception handling/catching in Blazor is not very mature yet, so maybe something is just going wrong there?

ok thank your help, i will migrate to 5.0.0-preview2, it seems to be resolve my issue

[larsk2009]

It seems like this has been solved, so I will close this issue. If it isn't fixed yet, let us know!