DKNet

Redirect the connection string to a real namespace

Part of Aspire.Hosting.ServiceBus. ServiceBusResource implements IResourceWithConnectionString, and both of its connection-string members check for a ConnectionStringRedirectAnnotation before falling back to the emulator’s own value — so a referencing project can be pointed at a real Azure Service Bus namespace without changing its own code.

using Aspire.Hosting;
using Aspire.Hosting.ApplicationModel;
using Aspire.Hosting.ServiceBus;

var builder = DistributedApplication.CreateBuilder(args);

var sql = builder.AddSqlServer("sql");
var serviceBus = builder.AddServiceBus(sql, configFilePath: "servicebus-config.json");

if (builder.ExecutionContext.IsPublishMode)
{
    var realNamespace = builder.AddConnectionString("real-service-bus");
    serviceBus.Resource.Annotations.Add(new ConnectionStringRedirectAnnotation(realNamespace.Resource));
}

builder.AddProject("api", "../Api/Api.csproj")
    .WithReference(serviceBus);

builder.Build().Run();

ConnectionStringExpression and GetConnectionStringAsync(CancellationToken) both call TryGetLastAnnotation<ConnectionStringRedirectAnnotation> first; when an annotation is present they return the annotated resource’s own expression or resolved value instead of building Endpoint=sb://{PrimaryEndpoint.Host};SharedAccessKeyName=RootManageSharedAccessKey;SharedAccessKey=SAS_KEY_VALUE;UseDevelopmentEmulator=true;.

🧱 Where it fits

The redirect only changes which string a referencing project receives through WithReference. AddServiceBus still provisions the full emulator resource — the container, the SQL Server dependency and WaitFor, the config bind mount — regardless of whether a redirect is applied; nothing short-circuits that wiring. See index.md for what else AddServiceBus adds alongside the resource this annotation targets.

⚠️ Gotchas & limits

• The emulator is still provisioned. Applying a redirect does not skip adding the emulator container, its SQL Server dependency, or the config bind mount — only the two connection-string members change what they return.
• PrimaryEndpoint is never redirected. It always resolves to the emulator’s own endpoint, even when ConnectionStringExpression points elsewhere.
• The annotation is read on every call. There is no caching of the redirect decision — TryGetLastAnnotation runs fresh each time ConnectionStringExpression or GetConnectionStringAsync is evaluated, so adding or removing the annotation changes the result from that point on.
• No built-in Azure Service Bus resource type. This package provisions the emulator only; wiring a ConnectionStringRedirectAnnotation to a real namespace is left entirely to the host application — there is no first-party “real Service Bus” resource type here to redirect to.

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