Azure.Messaging.ServiceBus (.NET)

Enterprise messaging SDK for reliable message delivery with queues, topics, subscriptions, and sessions.

Installation

bash
dotnet add package Azure.Messaging.ServiceBus
dotnet add package Azure.Identity

Current Version: v7.20.1 (stable)

Environment Variables

bash
AZURE_SERVICEBUS_FULLY_QUALIFIED_NAMESPACE=<namespace>.servicebus.windows.net  # Required: Service Bus fully qualified namespace
AZURE_TOKEN_CREDENTIALS=prod  # Required only if DefaultAzureCredential is used in production
AZURE_SERVICEBUS_CONNECTION_STRING=Endpoint=sb://...  # Alternative to Entra ID auth

Authentication

Microsoft Entra Token Credential

csharp
using Azure.Identity;
using Azure.Messaging.ServiceBus;

string fullyQualifiedNamespace = "<namespace>.servicebus.windows.net";
// Local dev: DefaultAzureCredential. Production: set AZURE_TOKEN_CREDENTIALS=prod or AZURE_TOKEN_CREDENTIALS=<specific_credential>
var credential = new DefaultAzureCredential(
    DefaultAzureCredential.DefaultEnvironmentVariableName
);
// Or use a specific credential directly in production:
// See https://learn.microsoft.com/dotnet/api/overview/azure/identity-readme?view=azure-dotnet#credential-classes
// var credential = new ManagedIdentityCredential();
await using ServiceBusClient client = new(fullyQualifiedNamespace, credential);

Connection String

csharp
string connectionString = "<connection_string>";
await using ServiceBusClient client = new(connectionString);

ASP.NET Core Dependency Injection

csharp
services.AddAzureClients(builder =>
{
    builder.AddServiceBusClientWithNamespace("<namespace>.servicebus.windows.net");
    builder.UseCredential(new DefaultAzureCredential());
});

Client Hierarchy

ServiceBusClient
├── CreateSender(queueOrTopicName)      → ServiceBusSender
├── CreateReceiver(queueName)           → ServiceBusReceiver
├── CreateReceiver(topicName, subName)  → ServiceBusReceiver
├── AcceptNextSessionAsync(queueName)   → ServiceBusSessionReceiver
├── CreateProcessor(queueName)          → ServiceBusProcessor
└── CreateSessionProcessor(queueName)   → ServiceBusSessionProcessor

ServiceBusAdministrationClient (separate client for CRUD)

Core Workflows

1. Send Messages

csharp
await using ServiceBusClient client = new(fullyQualifiedNamespace, new DefaultAzureCredential());
ServiceBusSender sender = client.CreateSender("my-queue");

// Single message
ServiceBusMessage message = new("Hello world!");
await sender.SendMessageAsync(message);

// Safe batching (recommended)
using ServiceBusMessageBatch batch = await sender.CreateMessageBatchAsync();
if (batch.TryAddMessage(new ServiceBusMessage("Message 1")))
{
    // Message added successfully
}
if (batch.TryAddMessage(new ServiceBusMessage("Message 2")))
{
    // Message added successfully
}
await sender.SendMessagesAsync(batch);

2. Receive Messages

csharp
ServiceBusReceiver receiver = client.CreateReceiver("my-queue");

// Single message
ServiceBusReceivedMessage message = await receiver.ReceiveMessageAsync();
string body = message.Body.ToString();
Console.WriteLine(body);

// Complete the message (removes from queue)
await receiver.CompleteMessageAsync(message);

// Batch receive
IReadOnlyList<ServiceBusReceivedMessage> messages = await receiver.ReceiveMessagesAsync(maxMessages: 10);
foreach (var msg in messages)
{
    Console.WriteLine(msg.Body.ToString());
    await receiver.CompleteMessageAsync(msg);
}

3. Message Settlement

csharp
// Complete - removes message from queue
await receiver.CompleteMessageAsync(message);

// Abandon - releases lock, message can be received again
await receiver.AbandonMessageAsync(message);

// Defer - prevents normal receive, use ReceiveDeferredMessageAsync
await receiver.DeferMessageAsync(message);

// Dead Letter - moves to dead letter subqueue
await receiver.DeadLetterMessageAsync(message, "InvalidFormat", "Message body was not valid JSON");

4. Background Processing with Processor

csharp
ServiceBusProcessor processor = client.CreateProcessor("my-queue", new ServiceBusProcessorOptions
{
    AutoCompleteMessages = false,
    MaxConcurrentCalls = 2
});

processor.ProcessMessageAsync += async (args) =>
{
    try
    {
        string body = args.Message.Body.ToString();
        Console.WriteLine($"Received: {body}");
        await args.CompleteMessageAsync(args.Message);
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Error processing: {ex.Message}");
        await args.AbandonMessageAsync(args.Message);
    }
};

processor.ProcessErrorAsync += (args) =>
{
    Console.WriteLine($"Error source: {args.ErrorSource}");
    Console.WriteLine($"Entity: {args.EntityPath}");
    Console.WriteLine($"Exception: {args.Exception}");
    return Task.CompletedTask;
};

await processor.StartProcessingAsync();
// ... application runs
await processor.StopProcessingAsync();

5. Sessions (Ordered Processing)

csharp
// Send session message
ServiceBusMessage message = new("Hello")
{
    SessionId = "order-123"
};
await sender.SendMessageAsync(message);

// Receive from next available session
ServiceBusSessionReceiver receiver = await client.AcceptNextSessionAsync("my-queue");

// Or receive from specific session
ServiceBusSessionReceiver receiver = await client.AcceptSessionAsync("my-queue", "order-123");

// Session state management
await receiver.SetSessionStateAsync(new BinaryData("processing"));
BinaryData state = await receiver.GetSessionStateAsync();

// Renew session lock
await receiver.RenewSessionLockAsync();

6. Dead Letter Queue

csharp
// Receive from dead letter queue
ServiceBusReceiver dlqReceiver = client.CreateReceiver("my-queue", new ServiceBusReceiverOptions
{
    SubQueue = SubQueue.DeadLetter
});

ServiceBusReceivedMessage dlqMessage = await dlqReceiver.ReceiveMessageAsync();

// Access dead letter metadata
string reason = dlqMessage.DeadLetterReason;
string description = dlqMessage.DeadLetterErrorDescription;
Console.WriteLine($"Dead letter reason: {reason} - {description}");

7. Topics and Subscriptions

csharp
// Send to topic
ServiceBusSender topicSender = client.CreateSender("my-topic");
await topicSender.SendMessageAsync(new ServiceBusMessage("Broadcast message"));

// Receive from subscription
ServiceBusReceiver subReceiver = client.CreateReceiver("my-topic", "my-subscription");
var message = await subReceiver.ReceiveMessageAsync();

8. Administration (CRUD)

csharp
var adminClient = new ServiceBusAdministrationClient(
    fullyQualifiedNamespace, 
    new DefaultAzureCredential());

// Create queue
var options = new CreateQueueOptions("my-queue")
{
    MaxDeliveryCount = 10,
    LockDuration = TimeSpan.FromSeconds(30),
    RequiresSession = true,
    DeadLetteringOnMessageExpiration = true
};
QueueProperties queue = await adminClient.CreateQueueAsync(options);

// Update queue
queue.LockDuration = TimeSpan.FromSeconds(60);
await adminClient.UpdateQueueAsync(queue);

// Create topic and subscription
await adminClient.CreateTopicAsync(new CreateTopicOptions("my-topic"));
await adminClient.CreateSubscriptionAsync(new CreateSubscriptionOptions("my-topic", "my-subscription"));

// Delete
await adminClient.DeleteQueueAsync("my-queue");

9. Cross-Entity Transactions

csharp
var options = new ServiceBusClientOptions { EnableCrossEntityTransactions = true };
await using var client = new ServiceBusClient(connectionString, options);

ServiceBusReceiver receiverA = client.CreateReceiver("queueA");
ServiceBusSender senderB = client.CreateSender("queueB");

ServiceBusReceivedMessage receivedMessage = await receiverA.ReceiveMessageAsync();

using (var ts = new TransactionScope(TransactionScopeAsyncFlowOption.Enabled))
{
    await receiverA.CompleteMessageAsync(receivedMessage);
    await senderB.SendMessageAsync(new ServiceBusMessage("Forwarded"));
    ts.Complete();
}

Key Types Reference

| Type | Purpose | |------|---------| | ServiceBusClient | Main entry point, manages connection | | ServiceBusSender | Sends messages to queues/topics | | ServiceBusReceiver | Receives messages from queues/subscriptions | | ServiceBusSessionReceiver | Receives session messages | | ServiceBusProcessor | Background message processing | | ServiceBusSessionProcessor | Background session processing | | ServiceBusAdministrationClient | CRUD for queues/topics/subscriptions | | ServiceBusMessage | Message to send | | ServiceBusReceivedMessage | Received message with metadata | | ServiceBusMessageBatch | Batch of messages |

Best Practices

1. Use singletons — Clients, senders, receivers, and processors are thread-safe
2. Always dispose — Use await using or call DisposeAsync()
3. Dispose order — Close senders/receivers/processors first, then client
4. Use DefaultAzureCredential — Prefer over connection strings for production
5. Use processors for background work — Handles lock renewal automatically
6. Use safe batching — CreateMessageBatchAsync() and TryAddMessage()
7. Handle transient errors — Use ServiceBusException.Reason
8. Configure transport — Use AmqpWebSockets if ports 5671/5672 are blocked
9. Set appropriate lock duration — Default is 30 seconds
10. Use sessions for ordering — FIFO within a session

Error Handling

csharp
try
{
    await sender.SendMessageAsync(message);
}
catch (ServiceBusException ex) when (ex.Reason == ServiceBusFailureReason.ServiceBusy)
{
    // Retry with backoff
}
catch (ServiceBusException ex)
{
    Console.WriteLine($"Service Bus Error: {ex.Reason} - {ex.Message}");
}

Related SDKs

| SDK | Purpose | Install | |-----|---------|---------| | Azure.Messaging.ServiceBus | Service Bus (this SDK) | dotnet add package Azure.Messaging.ServiceBus | | Azure.Messaging.EventHubs | Event streaming | dotnet add package Azure.Messaging.EventHubs | | Azure.Messaging.EventGrid | Event routing | dotnet add package Azure.Messaging.EventGrid |

Reference Links

| Resource | URL | |----------|-----| | NuGet Package | https://www.nuget.org/packages/Azure.Messaging.ServiceBus | | API Reference | https://learn.microsoft.com/dotnet/api/azure.messaging.servicebus | | GitHub Source | https://github.com/Azure/azure-sdk-for-net/tree/main/sdk/servicebus/Azure.Messaging.ServiceBus | | Troubleshooting | https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/servicebus/Azure.Messaging.ServiceBus/TROUBLESHOOTING.md |