microsoft/aspire · error · InvalidOperationException

Connection string is not initialized.

Error message

Connection string is not initialized.

What it means

AddBlobContainer registers a health check that lazily creates a BlobServiceClient from a connection string captured via a callback. The `connectionString ?? throw` guard fires when the connection-string resolution callback never assigned a value, meaning the resource was never bound to a real storage connection.

Solutions

1. Call AddBlobContainer on a resource created via AddAzureStorage (or another storage resource with a valid connection string)
2. Ensure the parent storage resource is running and healthy before this health check executes
3. Check the connection string callback/reference wired to the resource returns a non-empty value

Example fix

// before
var blobs = builder.AddBlobContainer("container", parent: unboundResource);
// after
var storage = builder.AddAzureStorage("storage");
var blobs = storage.AddBlobs("blobs").AddBlobContainer("container");

if (parentResource is null || parentResource.ConnectionStringResource is null)
    throw new InvalidOperationException("Blob container parent must have a connection string resource.");

When it happens

Trigger: Calling builder.AddBlobContainer(...) on a resource whose ConnectionStringResource / connection string callback returned null when the health check factory executed.

Common situations: Creating a blob container resource without a parent storage resource connection; referencing a storage resource that failed to start; typos in the referenced resource name so the callback never resolves.

Understand the failure class

Background: "missing required config value" errors: why libraries refuse to start when a configuration key is empty, unset, or blank — this error's family across 48 libraries.

Related errors

• BlobServiceClient is not initialized.
• Connection string is unavailable
• Connection string is unavailable
• Connection string is unavailable
• Connection string is unavailable

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/01213c00004f5547. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Hosting.Azure.Storage/AzureStorageExtensions.cs:502

    [AspireExport]
    public static IResourceBuilder<AzureBlobStorageContainerResource> AddBlobContainer(this IResourceBuilder<AzureStorageResource> builder, [ResourceName] string name, string? blobContainerName = null)
    {
        ArgumentNullException.ThrowIfNull(builder);
        ArgumentException.ThrowIfNullOrEmpty(name);

        blobContainerName ??= name;

        var parentBuilder = builder.Resource.ImplicitBlobService ??= GetBlobService(builder);
        AzureBlobStorageContainerResource resource = new(name, blobContainerName, parentBuilder.Resource);
        builder.Resource.BlobContainers.Add(resource);

        string? connectionString = null;

        var healthCheckKey = $"{resource.Name}_check";

        BlobServiceClient? blobServiceClient = null;
        builder.ApplicationBuilder.Services.AddHealthChecks().AddAzureBlobStorage(
            sp => blobServiceClient ??= CreateBlobServiceClient(connectionString ?? throw new InvalidOperationException("Connection string is not initialized.")),
            optionsFactory: sp => new HealthChecks.Azure.Storage.Blobs.AzureBlobStorageHealthCheckOptions { ContainerName = blobContainerName },
            name: healthCheckKey);

        return builder.ApplicationBuilder
            .AddResource(resource)
            .WithIconName("FolderOpen")
            .WithHealthCheck(healthCheckKey)
            .OnConnectionStringAvailable(async (containerResource, @event, ct) =>
            {
                connectionString = await resource.Parent.ConnectionStringExpression.GetValueAsync(ct).ConfigureAwait(false);
            });
    }

    /// <summary>
    /// Creates a builder for the <see cref="AzureDataLakeStorageFileSystemResource"/> which can be referenced to get the Azure DataLake file system connection string.
    /// </summary>
    /// <ats-summary>Adds an Azure Data Lake Storage file system resource</ats-summary>
    /// <param name="builder">The <see cref="IResourceBuilder{T}"/> for <see cref="AzureStorageResource"/>.</param>

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