Get started with Service Bus queues

In this tutorial, you create .NET Core console applications to send messages to and receive messages from a Service Bus queue.

Prerequisites

  1. Visual Studio 2017 Update 3 (version 15.3, 26730.01) or later.
  2. NET Core SDK, version 2.0 or later.
  3. An Azure subscription. To complete this tutorial, you need an Azure account. You can activate your MSDN subscriber benefits or sign up for a free account.
  4. If you don't have a queue to work with, follow steps in the Use Azure portal to create a Service Bus queue article to create a queue.
    1. Read the quick overview of Service Bus queues.
    2. Create a Service Bus namespace.
    3. Get the connection string.
    4. Create a Service Bus queue.

Send messages to the queue

To send messages to the queue, write a C# console application using Visual Studio.

Create a console application

Launch Visual Studio and create a new Console App (.NET Core) project.

Add the Service Bus NuGet package

  1. Right-click the newly created project and select Manage NuGet Packages.

  2. Click the Browse tab, search for Microsoft.Azure.ServiceBus, and then select the Microsoft.Azure.ServiceBus item. Click Install to complete the installation, then close this dialog box.

    Select a NuGet package

Write code to send messages to the queue

  1. In Program.cs, add the following using statements at the top of the namespace definition, before the class declaration:

    using System.Text;
    using System.Threading;
    using System.Threading.Tasks;
    using Microsoft.Azure.ServiceBus;
    
  2. Within the Program class, declare the following variables. Set the ServiceBusConnectionString variable to the connection string that you obtained when creating the namespace, and set QueueName to the name that you used when creating the queue:

    const string ServiceBusConnectionString = "<your_connection_string>";
    const string QueueName = "<your_queue_name>";
    static IQueueClient queueClient;
    
  3. Replace the default contents of Main() with the following line of code:

    MainAsync().GetAwaiter().GetResult();
    
  4. Directly after Main(), add the following asynchronous MainAsync() method that calls the send messages method:

    static async Task MainAsync()
    {
        const int numberOfMessages = 10;
        queueClient = new QueueClient(ServiceBusConnectionString, QueueName);
    
        Console.WriteLine("======================================================");
        Console.WriteLine("Press ENTER key to exit after sending all the messages.");
        Console.WriteLine("======================================================");
    
        // Send messages.
        await SendMessagesAsync(numberOfMessages);
    
        Console.ReadKey();
    
        await queueClient.CloseAsync();
    }
    
  5. Directly after the MainAsync() method, add the following SendMessagesAsync() method that performs the work of sending the number of messages specified by numberOfMessagesToSend (currently set to 10):

    static async Task SendMessagesAsync(int numberOfMessagesToSend)
    {
        try
        {
            for (var i = 0; i < numberOfMessagesToSend; i++)
            {
                // Create a new message to send to the queue.
                string messageBody = $"Message {i}";
                var message = new Message(Encoding.UTF8.GetBytes(messageBody));
    
                // Write the body of the message to the console.
                Console.WriteLine($"Sending message: {messageBody}");
    
                // Send the message to the queue.
                await queueClient.SendAsync(message);
            }
        }
        catch (Exception exception)
        {
            Console.WriteLine($"{DateTime.Now} :: Exception: {exception.Message}");
        }
    }
    
  6. Here is what your Program.cs file should look like.

    namespace CoreSenderApp
    {
        using System;
        using System.Text;
        using System.Threading;
        using System.Threading.Tasks;
        using Microsoft.Azure.ServiceBus;
    
        class Program
        {
            // Connection String for the namespace can be obtained from the Azure portal under the 
            // 'Shared Access policies' section.
            const string ServiceBusConnectionString = "<your_connection_string>";
            const string QueueName = "<your_queue_name>";
            static IQueueClient queueClient;
    
            static void Main(string[] args)
            {
                MainAsync().GetAwaiter().GetResult();
            }
    
            static async Task MainAsync()
            {
                const int numberOfMessages = 10;
                queueClient = new QueueClient(ServiceBusConnectionString, QueueName);
    
                Console.WriteLine("======================================================");
                Console.WriteLine("Press ENTER key to exit after sending all the messages.");
                Console.WriteLine("======================================================");
    
                // Send Messages
                await SendMessagesAsync(numberOfMessages);
    
                Console.ReadKey();
    
                await queueClient.CloseAsync();
            }
    
            static async Task SendMessagesAsync(int numberOfMessagesToSend)
            {
                try
                {
                    for (var i = 0; i < numberOfMessagesToSend; i++)
                    {
                        // Create a new message to send to the queue
                        string messageBody = $"Message {i}";
                        var message = new Message(Encoding.UTF8.GetBytes(messageBody));
    
                        // Write the body of the message to the console
                        Console.WriteLine($"Sending message: {messageBody}");
    
                        // Send the message to the queue
                        await queueClient.SendAsync(message);
                    }
                }
                catch (Exception exception)
                {
                    Console.WriteLine($"{DateTime.Now} :: Exception: {exception.Message}");
                }
            }
        }
    }
    
  7. Run the program, and check the Azure portal: click the name of your queue in the namespace Overview window. The queue Essentials screen is displayed. Notice that the Active Message Count value for the queue is now 10. Each time you run the sender application without retrieving the messages (as described in the next section), this value increases by 10. Also note that the current size of the queue increments the Current value in the Essentials window each time the app adds messages to the queue.

    Message size

Receive messages from the queue

To receive the messages you sent, create another .NET Core console application and install the Microsoft.Azure.ServiceBus NuGet package, similar to the previous sender application.

Write code to receive messages from the queue

  1. In Program.cs, add the following using statements at the top of the namespace definition, before the class declaration:

    using System.Text;
    using System.Threading;
    using System.Threading.Tasks;
    using Microsoft.Azure.ServiceBus;
    
  2. Within the Program class, declare the following variables. Set the ServiceBusConnectionString variable to the connection string that you obtained when creating the namespace, and set QueueName to the name that you used when creating the queue:

    const string ServiceBusConnectionString = "<your_connection_string>";
    const string QueueName = "<your_queue_name>";
    static IQueueClient queueClient;
    
  3. Replace the default contents of Main() with the following line of code:

    MainAsync().GetAwaiter().GetResult();
    
  4. Directly after Main(), add the following asynchronous MainAsync() method that calls the RegisterOnMessageHandlerAndReceiveMessages() method:

    static async Task MainAsync()
    {
        queueClient = new QueueClient(ServiceBusConnectionString, QueueName);
    
        Console.WriteLine("======================================================");
        Console.WriteLine("Press ENTER key to exit after receiving all the messages.");
        Console.WriteLine("======================================================");
    
        // Register the queue message handler and receive messages in a loop
        RegisterOnMessageHandlerAndReceiveMessages();
    
        Console.ReadKey();
    
        await queueClient.CloseAsync();
    }
    
  5. Directly after the MainAsync() method, add the following method that registers the message handler and receives the messages sent by the sender application:

    static void RegisterOnMessageHandlerAndReceiveMessages()
    {
        // Configure the message handler options in terms of exception handling, number of concurrent messages to deliver, etc.
        var messageHandlerOptions = new MessageHandlerOptions(ExceptionReceivedHandler)
        {
            // Maximum number of concurrent calls to the callback ProcessMessagesAsync(), set to 1 for simplicity.
            // Set it according to how many messages the application wants to process in parallel.
            MaxConcurrentCalls = 1,
    
            // Indicates whether the message pump should automatically complete the messages after returning from user callback.
            // False below indicates the complete operation is handled by the user callback as in ProcessMessagesAsync().
            AutoComplete = false
        };
    
        // Register the function that processes messages.
        queueClient.RegisterMessageHandler(ProcessMessagesAsync, messageHandlerOptions);
    }
    
  6. Directly after the previous method, add the following ProcessMessagesAsync() method to process the received messages:

    static async Task ProcessMessagesAsync(Message message, CancellationToken token)
    {
        // Process the message.
        Console.WriteLine($"Received message: SequenceNumber:{message.SystemProperties.SequenceNumber} Body:{Encoding.UTF8.GetString(message.Body)}");
    
        // Complete the message so that it is not received again.
        // This can be done only if the queue Client is created in ReceiveMode.PeekLock mode (which is the default).
        await queueClient.CompleteAsync(message.SystemProperties.LockToken);
    
        // Note: Use the cancellationToken passed as necessary to determine if the queueClient has already been closed.
        // If queueClient has already been closed, you can choose to not call CompleteAsync() or AbandonAsync() etc.
        // to avoid unnecessary exceptions.
    }
    
  7. Finally, add the following method to handle any exceptions that might occur:

    // Use this handler to examine the exceptions received on the message pump.
    static Task ExceptionReceivedHandler(ExceptionReceivedEventArgs exceptionReceivedEventArgs)
    {
        Console.WriteLine($"Message handler encountered an exception {exceptionReceivedEventArgs.Exception}.");
        var context = exceptionReceivedEventArgs.ExceptionReceivedContext;
        Console.WriteLine("Exception context for troubleshooting:");
        Console.WriteLine($"- Endpoint: {context.Endpoint}");
        Console.WriteLine($"- Entity Path: {context.EntityPath}");
        Console.WriteLine($"- Executing Action: {context.Action}");
        return Task.CompletedTask;
    }    
    
  8. Here is what your Program.cs file should look like:

    namespace CoreReceiverApp
    {
        using System;
        using System.Text;
        using System.Threading;
        using System.Threading.Tasks;
        using Microsoft.Azure.ServiceBus;
    
        class Program
        {
            // Connection String for the namespace can be obtained from the Azure portal under the 
            // 'Shared Access policies' section.
            const string ServiceBusConnectionString = "<your_connection_string>";
            const string QueueName = "<your_queue_name>";
            static IQueueClient queueClient;
    
            static void Main(string[] args)
            {
                MainAsync().GetAwaiter().GetResult();
            }
    
            static async Task MainAsync()
            {
                queueClient = new QueueClient(ServiceBusConnectionString, QueueName);
    
                Console.WriteLine("======================================================");
                Console.WriteLine("Press ENTER key to exit after receiving all the messages.");
                Console.WriteLine("======================================================");
    
                // Register QueueClient's MessageHandler and receive messages in a loop
                RegisterOnMessageHandlerAndReceiveMessages();
    
                Console.ReadKey();
    
                await queueClient.CloseAsync();
            }
    
            static void RegisterOnMessageHandlerAndReceiveMessages()
            {
                // Configure the MessageHandler Options in terms of exception handling, number of concurrent messages to deliver etc.
                var messageHandlerOptions = new MessageHandlerOptions(ExceptionReceivedHandler)
                {
                    // Maximum number of Concurrent calls to the callback `ProcessMessagesAsync`, set to 1 for simplicity.
                    // Set it according to how many messages the application wants to process in parallel.
                    MaxConcurrentCalls = 1,
    
                    // Indicates whether MessagePump should automatically complete the messages after returning from User Callback.
                    // False below indicates the Complete will be handled by the User Callback as in `ProcessMessagesAsync` below.
                    AutoComplete = false
                };
    
                // Register the function that will process messages
                queueClient.RegisterMessageHandler(ProcessMessagesAsync, messageHandlerOptions);
            }
    
            static async Task ProcessMessagesAsync(Message message, CancellationToken token)
            {
                // Process the message
                Console.WriteLine($"Received message: SequenceNumber:{message.SystemProperties.SequenceNumber} Body:{Encoding.UTF8.GetString(message.Body)}");
    
                // Complete the message so that it is not received again.
                // This can be done only if the queueClient is created in ReceiveMode.PeekLock mode (which is default).
                await queueClient.CompleteAsync(message.SystemProperties.LockToken);
    
                // Note: Use the cancellationToken passed as necessary to determine if the queueClient has already been closed.
                // If queueClient has already been Closed, you may chose to not call CompleteAsync() or AbandonAsync() etc. calls 
               // to avoid unnecessary exceptions.
            }
    
            static Task ExceptionReceivedHandler(ExceptionReceivedEventArgs exceptionReceivedEventArgs)
            {
                Console.WriteLine($"Message handler encountered an exception {exceptionReceivedEventArgs.Exception}.");
                var context = exceptionReceivedEventArgs.ExceptionReceivedContext;
                Console.WriteLine("Exception context for troubleshooting:");
                Console.WriteLine($"- Endpoint: {context.Endpoint}");
                Console.WriteLine($"- Entity Path: {context.EntityPath}");
                Console.WriteLine($"- Executing Action: {context.Action}");
                return Task.CompletedTask;
            }
        }
    }
    
  9. Run the program, and check the portal again. Notice that the Active Message Count and Current values are now 0.

    Queue length

Congratulations! You have now created a queue, sent a set of messages to that queue, and received those messages from the same queue.

Note

You can manage Service Bus resources with Service Bus Explorer. The Service Bus Explorer allows users to connect to a Service Bus namespace and administer messaging entities in an easy manner. The tool provides advanced features like import/export functionality or the ability to test topic, queues, subscriptions, relay services, notification hubs and events hubs.

Next steps

Check out our GitHub repository with samples that demonstrate some of the more advanced features of Service Bus messaging.