microsoft/aspire · error · ArgumentNullException

Value cannot be null. (Parameter 'logger')

Error message

Value cannot be null. (Parameter 'logger')

What it means

This obsolete ResourceNotificationService constructor requires a non-null ILogger<ResourceNotificationService>. Passing null fails fast via ArgumentNullException. The constructor exists only for backward compatibility and will be removed.

Solutions

1. Use the 4-parameter constructor (ILogger, IHostApplicationLifetime, IServiceProvider, ResourceLoggerService)
2. Register ILogger<T> in the DI container or use NullLogger<ResourceNotificationService>.Instance in tests
3. Remove direct construction and resolve the service from DI

Example fix

// before
new ResourceNotificationService(null, lifetime);
// after
new ResourceNotificationService(NullLogger<ResourceNotificationService>.Instance, lifetime,
    services, new ResourceLoggerService());

if (logger is null) logger = NullLogger<ResourceNotificationService>.Instance;

try { var svc = new ResourceNotificationService(logger, lifetime); }
catch (ArgumentNullException) { /* supply a logger or migrate to the DI constructor */ }

When it happens

Trigger: Calling new ResourceNotificationService(null, hostApplicationLifetime) or passing a null logger from legacy host-building code.

Common situations: Migrating old code that previously constructed the service manually; DI containers supplying null due to missing ILogger registrations.

Related errors

• adminPassword
• Array params contains null item
• Value cannot be null. (Parameter 'iconName')
• Value cannot be null. (Parameter 'innerResource')
• Value cannot be null. (Parameter 'resource')

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/174c065d49ac3229. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/ApplicationModel/ResourceNotificationService.cs:55

    internal WaitBehavior DefaultWaitBehavior { get; set; }

    /// <summary>
    /// Creates a new instance of <see cref="ResourceNotificationService"/>.
    /// </summary>
    /// <remarks>
    /// Obsolete. Use the constructor that accepts an <see cref="ILogger{ResourceNotificationService}"/>, <see cref="IHostApplicationLifetime"/> and <see cref="IServiceProvider"/>.<br/>
    /// This constructor will be removed in the next major version of Aspire.
    /// </remarks>
    /// <param name="logger">The logger.</param>
    /// <param name="hostApplicationLifetime">The host application lifetime.</param>
    [Obsolete($"""
        {nameof(ResourceNotificationService)} now requires an {nameof(IServiceProvider)} and {nameof(ResourceLoggerService)}.
        Use the constructor that accepts an {nameof(ILogger)}<{nameof(ResourceNotificationService)}>, {nameof(IHostApplicationLifetime)}, {nameof(IServiceProvider)} and {nameof(ResourceLoggerService)}.
        This constructor will be removed in the next major version of Aspire.
        """)]
    public ResourceNotificationService(ILogger<ResourceNotificationService> logger, IHostApplicationLifetime hostApplicationLifetime)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        _serviceProvider = new NullServiceProvider();
        _resourceLoggerService = new ResourceLoggerService();
        DefaultWaitBehavior = WaitBehavior.StopOnResourceUnavailable;
    }

    /// <summary>
    /// Creates a new instance of <see cref="ResourceNotificationService"/>.
    /// </summary>
    /// <param name="logger">The logger.</param>
    /// <param name="hostApplicationLifetime">The host application lifetime.</param>
    /// <param name="resourceLoggerService">The resource logger service.</param>
    /// <param name="serviceProvider">The service provider.</param>
    public ResourceNotificationService(
        ILogger<ResourceNotificationService> logger,
        IHostApplicationLifetime hostApplicationLifetime,
        IServiceProvider serviceProvider,
        ResourceLoggerService resourceLoggerService)
    {

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