microsoft/aspire · error · ArgumentException

Application Insights must be omitted, a location string, a…

Error message

Application Insights must be omitted, a location string, a location parameter, or an Application Insights resource builder.

What it means

WithAzureApplicationInsightsForPolyglot accepts a loosely-typed object for Application Insights configuration (omitted, a location string, a location parameter, or a resource builder). The switch expression's discard arm throws ArgumentException when the value's runtime type matches none of the supported shapes.

Solutions

1. Pass null to use defaults, a string location like "eastus", an IResourceBuilder<ParameterResource>, or an IResourceBuilder<AzureApplicationInsightsResource>.
2. If you have a ParameterResource, pass it through its IResourceBuilder<ParameterResource> wrapper.
3. If you have an AzureApplicationInsightsResource, get it from its IResourceBuilder instead of passing the raw resource.
4. At the call site, convert/validate the argument's type before invoking the polyglot API.

Example fix

// before
env.WithAzureApplicationInsightsForPolyglot(appInsightsResource); // raw resource
// after
env.WithAzureApplicationInsightsForPolyglot(appInsightsBuilder); // IResourceBuilder<AzureApplicationInsightsResource>

var ok = applicationInsights is null or string or IResourceBuilder<ParameterResource> or IResourceBuilder<AzureApplicationInsightsResource>;

static bool IsValidAppInsightsArg(object? v) => v is null or string or IResourceBuilder<ParameterResource> or IResourceBuilder<AzureApplicationInsightsResource>;

try { env.WithAzureApplicationInsightsForPolyglot(applicationInsights); } catch (ArgumentException ex) { logger.LogError(ex, "Unsupported Application Insights argument type {Type}", applicationInsights?.GetType().Name); }

When it happens

Trigger: Passing an unsupported type to WithAzureApplicationInsightsForPolyglot — e.g. an int, a ParameterResource directly (unwrapped by IResourceBuilder<>), an AzureApplicationInsightsResource without its builder wrapper, or an IResourceBuilder of some other resource type.

Common situations: Polyglot (non-C#) callers supplying JSON/YAML values that deserialize to the wrong type; C# callers passing a resource instead of a resource builder; dynamic/reflective wrappers boxing the argument into object with an unexpected concrete type.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Deployment slot must be a string or a parameter resource…
• Address prefix must be a string or a parameter resource…
• Address prefix must be omitted, a string, or a parameter…
• App Service configuration validation failed. See errors…
• App Service context not found for resource

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/17107370ac9102df. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.Azure.AppService/AzureAppServiceEnvironmentExtensions.cs:380

    }

    /// <summary>
    /// Enables Azure Application Insights for the Azure App Service environment
    /// </summary>
    [AspireExport("withAzureApplicationInsights")]
    internal static IResourceBuilder<AzureAppServiceEnvironmentResource> WithAzureApplicationInsightsForPolyglot(
        this IResourceBuilder<AzureAppServiceEnvironmentResource> builder,
        [AspireUnion(typeof(string), typeof(IResourceBuilder<ParameterResource>), typeof(IResourceBuilder<AzureApplicationInsightsResource>))] object? applicationInsights = null)
    {
        ArgumentNullException.ThrowIfNull(builder);

        return applicationInsights switch
        {
            null => builder.WithAzureApplicationInsights(),
            string applicationInsightsLocation => builder.WithAzureApplicationInsights(applicationInsightsLocation),
            IResourceBuilder<ParameterResource> applicationInsightsLocationParameter => builder.WithAzureApplicationInsights(applicationInsightsLocationParameter),
            IResourceBuilder<AzureApplicationInsightsResource> applicationInsightsBuilder => builder.WithAzureApplicationInsights(applicationInsightsBuilder),
            _ => throw new ArgumentException(
                "Application Insights must be omitted, a location string, a location parameter, or an Application Insights resource builder.",
                nameof(applicationInsights))
        };
    }

    /// <summary>
    /// Configures whether Azure Application Insights should be enabled for the Azure App Service.
    /// </summary>
    /// <param name="builder">The AzureAppServiceEnvironmentResource to configure.</param>
    /// <param name="applicationInsightsLocation">The location for Application Insights.</param>
    /// <returns><see cref="IResourceBuilder{T}"/></returns>
    [AspireExportIgnore(Reason = "Polyglot AppHosts use the internal withAzureApplicationInsights dispatcher export.")]
    public static IResourceBuilder<AzureAppServiceEnvironmentResource> WithAzureApplicationInsights(this IResourceBuilder<AzureAppServiceEnvironmentResource> builder, string applicationInsightsLocation)
    {
        builder.WithAzureApplicationInsights();
        builder.Resource.ApplicationInsightsLocation = applicationInsightsLocation;
        return builder;
    }

View on GitHub (pinned to 25830f84bd)