dotnet/orleans · error · ArgumentNullException

Value cannot be null. (Parameter 'createClientCallback')

Error message

Value cannot be null. (Parameter 'createClientCallback')

What it means

Thrown by AzureBlobJournalStorageOptions.ConfigureBlobServiceClient(Func<...>) when the createClientCallback argument is null. The callback is stored as the factory used to lazily create a BlobServiceClient; a null callback would cause a NullReferenceException later during storage initialization, so it is rejected immediately.

Source

Thrown at src/Azure/Orleans.Journaling.AzureStorage/AzureBlobJournalStorageOptions.cs:172

        ArgumentException.ThrowIfNullOrWhiteSpace(connectionString);
        CreateClient = ct => Task.FromResult(new BlobServiceClient(connectionString, ClientOptions));
    }

    /// <summary>
    /// Configures the <see cref="BlobServiceClient"/> using an authenticated service URI.
    /// </summary>
    public void ConfigureBlobServiceClient(Uri serviceUri)
    {
        ArgumentNullException.ThrowIfNull(serviceUri);
        CreateClient = ct => Task.FromResult(new BlobServiceClient(serviceUri, ClientOptions));
    }

    /// <summary>
    /// Configures the <see cref="BlobServiceClient"/> using the provided callback.
    /// </summary>
    public void ConfigureBlobServiceClient(Func<CancellationToken, Task<BlobServiceClient>> createClientCallback)
    {
        CreateClient = createClientCallback ?? throw new ArgumentNullException(nameof(createClientCallback));
    }

    /// <summary>
    /// Configures the <see cref="BlobServiceClient"/> using an authenticated service URI and a <see cref="TokenCredential"/>.
    /// </summary>
    public void ConfigureBlobServiceClient(Uri serviceUri, TokenCredential tokenCredential)
    {
        ArgumentNullException.ThrowIfNull(serviceUri);
        ArgumentNullException.ThrowIfNull(tokenCredential);
        CreateClient = ct => Task.FromResult(new BlobServiceClient(serviceUri, tokenCredential, ClientOptions));
    }

    /// <summary>
    /// Configures the <see cref="BlobServiceClient"/> using an authenticated service URI and a <see cref="AzureSasCredential"/>.
    /// </summary>
    public void ConfigureBlobServiceClient(Uri serviceUri, AzureSasCredential azureSasCredential)
    {
        ArgumentNullException.ThrowIfNull(serviceUri);

View on GitHub (pinned to fca799fa70)

Solutions

Pass a non-null callback, e.g. options.ConfigureBlobServiceClient(ct => Task.FromResult(new BlobServiceClient(connectionString))).
If you do not need a custom factory, use one of the other ConfigureBlobServiceClient overloads (connection string, Uri, or Uri+credential).
Prefer setting BlobServiceClient directly rather than a factory when the client is already constructed.

Example fix

// before
Func<CancellationToken, Task<BlobServiceClient>> factory = null!;
options.ConfigureBlobServiceClient(factory);

// after
options.ConfigureBlobServiceClient(ct => Task.FromResult(new BlobServiceClient(connectionString)));

Defensive patterns

Strategy: validation

Validate before calling

if (createClientCallback is null) throw new ArgumentNullException(nameof(createClientCallback));
options.ConfigureBlobServiceClient(createClientCallback);

Prevention

Prefer the BlobServiceClient property setter or connection-string overload over a raw callback.
Enable nullable reference types so null callbacks are caught at compile time.
Pass a lambda directly rather than an uninitialized delegate field.

When it happens

Trigger: Calling options.ConfigureBlobServiceClient((Func<CancellationToken, Task<BlobServiceClient>>)null). The null-coalescing throw runs before assignment.

Common situations: Passing an uninitialized delegate field; a conditional expression that evaluates to null; refactoring that accidentally drops the lambda.

Related errors

AI-assisted analysis of dotnet/orleans@fca799fa70 (2026-08-13). Data as JSON: /api/errors/fd6caf8c6db33504. Report an issue: GitHub.