microsoft/aspire · error · ArgumentException

Unsupported Bing reference type

Error message

Unsupported Bing reference type '{bingReference.GetType().Name}'. Expected IResourceBuilder<BingGroundingConnectionResource>, string, or IResourceBuilder<ParameterResource>.

What it means

The Bing Grounding WithReference overload accepts only an IResourceBuilder<BingGroundingConnectionResource>, a string (connection name), or an IResourceBuilder<ParameterResource>. Any other object falls into the switch's default case and raises this ArgumentException naming the actual runtime type received.

Solutions

Pass one of the accepted types: a Bing connection resource builder, a string connection name, or a parameter resource builder.
If you have a connection string, wrap it in a parameter resource: builder.AddParameter("bing-key") and pass that builder.
Check the PromptAgentBuilderExtensions API docs for the exact accepted overloads.

Example fix

// before
bingTool.WithReference("https://my-bing-endpoint");
// after
var bingParam = builder.AddParameter("bing-connection");
bingTool.WithReference(bingParam);

Defensive patterns

Strategy: type-guard

Validate before calling

if (bingRef is not IResourceBuilder<BingGroundingConnectionResource> && bingRef is not string && bingRef is not IResourceBuilder<ParameterResource>) throw new ArgumentException(nameof(bingRef));

Type guard

static bool IsValidBingReference(object bingRef) =>
    bingRef is IResourceBuilder<BingGroundingConnectionResource>
    || bingRef is string
    || bingRef is IResourceBuilder<ParameterResource>;

Try / catch

try
{
    bingTool.WithReference(bingRef);
}
catch (ArgumentException ex)
{
    logger.LogError(ex, "Unsupported Bing reference type {Type}", bingRef.GetType().Name);
    throw;
}

Prevention

Pass a Bing connection resource builder, string, or parameter resource builder — nothing else.
Wrap raw connection strings in AddParameter before referencing.
Check the WithReference overload signature in PromptAgentBuilderExtensions when unsure.

When it happens

Trigger: Passing an unsupported argument type to WithReference on a Bing tool — e.g. IResourceBuilder<ParameterResource> confusion with a raw ParameterResource, a connection string value, or an unrelated resource builder.

Common situations: Misreading the overload's contract and passing a connection string literal or a different resource type; refactors that change argument types without updating call sites.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/930a04a72e3a28f3. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.Foundry/PromptAgent/PromptAgentBuilderExtensions.cs:473

            case IResourceBuilder<BingGroundingConnectionResource> connectionBuilder:
                tool.Resource.Connection = connectionBuilder.Resource;
                break;

            case string bingResourceId:
                ArgumentException.ThrowIfNullOrEmpty(bingResourceId);
                var projectBuilder = tool.ApplicationBuilder.CreateResourceBuilder(tool.Resource.Project);
                var connection = projectBuilder.AddBingGroundingConnection($"{tool.Resource.Name}-conn", bingResourceId);
                tool.Resource.Connection = connection.Resource;
                break;

            case IResourceBuilder<ParameterResource> parameterBuilder:
                var paramProjectBuilder = tool.ApplicationBuilder.CreateResourceBuilder(tool.Resource.Project);
                var paramConnection = paramProjectBuilder.AddBingGroundingConnection($"{tool.Resource.Name}-conn", parameterBuilder);
                tool.Resource.Connection = paramConnection.Resource;
                break;

            default:
                throw new ArgumentException(
                    $"Unsupported Bing reference type '{bingReference.GetType().Name}'. " +
                    "Expected IResourceBuilder<BingGroundingConnectionResource>, string, or IResourceBuilder<ParameterResource>.",
                    nameof(bingReference));
        }

        return tool;
    }

    // ──────────────────────────────────────────────────────────────
    // Configuration-only tools
    // ──────────────────────────────────────────────────────────────

    /// <summary>
    /// Adds a SharePoint grounding tool to a Microsoft Foundry project, enabling agents to
    /// search data from SharePoint sites configured as Foundry project connections.
    /// </summary>
    /// <param name="project">The <see cref="IResourceBuilder{T}"/> for the Microsoft Foundry project.</param>
    /// <ats-param name="project">The Microsoft Foundry project resource builder.</ats-param>

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