microsoft/aspire · error · InvalidOperationException

Resource is not set. This callback context is not…

Error message

Resource is not set. This callback context is not associated with a resource.

What it means

EnvironmentCallbackContext.Resource is optional at construction but many callbacks require the resource. Accessing Resource when the context was created without one throws this InvalidOperationException, since the context is then not associated with any resource.

Solutions

Pass the IResource when constructing EnvironmentCallbackContext so Resource is set
In shared/global callbacks, avoid accessing Resource, or guard with a null-check on the underlying _resource before use
In tests, always supply a concrete resource (e.g., a GeneratedResource) when building the context

Example fix

// before
var ctx = new EnvironmentCallbackContext(executionContext);
ctx.Resource.Annotations.Add(...); // throws
// after
var ctx = new EnvironmentCallbackContext(executionContext, resource: myResource);
ctx.Resource.Annotations.Add(...);

Defensive patterns

Strategy: type-guard

Validate before calling

// resource presence can be checked via the context's constructor parameters; prefer constructing with a resource:
// new EnvironmentCallbackContext(executionContext, resource: resource, cancellationToken: ct)

Type guard

bool TryGetResource(EnvironmentCallbackContext ctx, out IResource? resource) => (resource = ctx is { } c && c.ToString() is not null ? null : null) is not null; // Resource getter throws by design; construct with a resource instead

Try / catch

try { var res = context.Resource; } catch (InvalidOperationException ex) when (ex.Message.Contains("Resource is not set")) { /* this context has no resource; skip resource-specific work */ }

Prevention

Always construct EnvironmentCallbackContext with the resource parameter
In shared/global callbacks, do not access Resource
In unit tests, pass a real or generated resource when building contexts

When it happens

Trigger: Calling ctx.Resource inside an EnvironmentCallback that was registered globally or invoked with a context constructed via the constructor overload without a resource (e.g., manually created contexts in tests or shared/global environment callbacks).

Common situations: Manually constructing EnvironmentCallbackContext in unit tests without passing the resource; callbacks added via ConfigureAllRetrievedEnvironment-style APIs where no single resource exists but code still touches Resource.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/12ba772eaa396f74. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting/ApplicationModel/EnvironmentCallbackContext.cs:69

    /// </summary>
    [AspireExport]
    internal EnvironmentEditor Environment => new(EnvironmentVariables);

    /// <summary>
    /// Gets the logger facade used by polyglot callbacks.
    /// </summary>
    [AspireExport]
    internal LogFacade Log => new(() => Logger);

    /// <summary>
    /// The resource associated with this callback context.
    /// </summary>
    /// <remarks>
    /// This will be set to the resource in all cases where Aspire invokes the callback.
    /// </remarks>
    /// <exception cref="InvalidOperationException">Thrown when the EnvironmentCallbackContext was created without a specified resource.</exception>
    [AspireExport]
    public IResource Resource => _resource ?? throw new InvalidOperationException($"{nameof(Resource)} is not set. This callback context is not associated with a resource.");

    /// <summary>
    /// Gets the execution context associated with this invocation of the AppHost.
    /// </summary>
    [AspireExport]
    public DistributedApplicationExecutionContext ExecutionContext { get; } = executionContext ?? throw new ArgumentNullException(nameof(executionContext));
}

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