HangfireIO/Hangfire · error · ArgumentNullException

execution

Error message

execution

What it means

Thrown by BackgroundDispatcherAsync's constructor (internal) when the IBackgroundExecution argument is null. The dispatcher delegates all work (RunAsync) to that execution, so a null instance has nothing to drive.

Source

Thrown at src/Hangfire.Core/Processing/BackgroundDispatcherAsync.cs:49

        private readonly IBackgroundExecution _execution;
        private readonly Func<Guid, object, Task> _action;
        private readonly object _state;

        private readonly TaskScheduler _taskScheduler;
        private readonly bool _ownsScheduler;

        public BackgroundDispatcherAsync(
            [NotNull] IBackgroundExecution execution,
            [NotNull] Func<Guid, object, Task> action,
            [CanBeNull] object state,
            [NotNull] TaskScheduler taskScheduler,
            int maxConcurrency,
            bool ownsScheduler)
        {
            if (maxConcurrency <= 0) throw new ArgumentOutOfRangeException(nameof(maxConcurrency));

            _execution = execution ?? throw new ArgumentNullException(nameof(execution));
            _action = action ?? throw new ArgumentNullException(nameof(action));
            _state = state;
            _taskScheduler = taskScheduler ?? throw new ArgumentNullException(nameof(taskScheduler));
            _ownsScheduler = ownsScheduler;

#if !NETSTANDARD1_3
            AppDomainUnloadMonitor.EnsureInitialized();
#endif

            _stopped = new CountdownEvent(maxConcurrency);

            for (var i = 0; i < maxConcurrency; i++)
            {
                Task.Factory.StartNew(
                    DispatchLoop,
                    CancellationToken.None,
                    TaskCreationOptions.None,
                    _taskScheduler).Unwrap();

View on GitHub (pinned to c236dd0f93)

Solutions

1. Ensure a non-null IBackgroundExecution (BackgroundExecution instance) is created and passed.
2. Guard the call site with a null check and fail fast with a clearer message before reaching the constructor.
3. Verify the dependency-injection registration that supplies the execution is active and not returning null.

Example fix

// before
var dispatcher = new BackgroundDispatcherAsync(null, action, state, scheduler, 4, false);

// after
var execution = execution ?? throw new InvalidOperationException("Execution must be initialized before the dispatcher.");
var dispatcher = new BackgroundDispatcherAsync(execution, action, state, scheduler, 4, false);

if (execution == null) throw new InvalidOperationException("IBackgroundExecution must be created before the dispatcher.");

When it happens

Trigger: Constructing BackgroundDispatcherAsync with execution == null. Internal wiring that failed to create/resolve the BackgroundExecution dependency before building the dispatcher.

Common situations: DI/registration defect where the execution instance was not created; a null propagated from a factory method that returned null on a missing storage dependency; unit test stubbing that forgot to supply the execution.

Related errors

• taskScheduler
• options
• callback
• value
• waitHandle

AI-assisted analysis of HangfireIO/Hangfire@c236dd0f93 (2026-08-13). Data as JSON: /api/errors/e253e8f15858e216. Report an issue: GitHub.