Get started with Service Bus queues

• 01/24/2020
• 7 minutes to read
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In this tutorial, you create .NET Core console applications to send messages to and receive messages from a Service Bus queue.

Prerequisites

• Visual Studio 2019.

• NET Core SDK, version 2.0 or later.

• 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.

• 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.

  • Read the quick overview of Service Bus queues.
  • Create a Service Bus namespace.
  • Get the connection string.
  • 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 for C#. This example names the app CoreSenderApp.

Add the Service Bus NuGet package

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

2. Select Browse. Search for and select Microsoft.Azure.ServiceBus.

3. Select Install to complete the installation, then close the NuGet Package Manager.

   

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. In the Program class, declare the following variables:

   const string ServiceBusConnectionString = "<your_connection_string>";
   const string QueueName = "<your_queue_name>";
   static IQueueClient queueClient;
   

   Enter your connection string for the namespace as the ServiceBusConnectionString variable. Enter your queue name.

3. Replace the Main() method with the following async Main method. It calls the SendMessagesAsync() method that you will add in the next step to send messages to the queue.

   public static async Task Main(string[] args)
   {    
       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();
   }
   

4. Directly after the MainAsync() method, add the following SendMessagesAsync() method that does 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}");
       }
   }
   

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;

        public static async Task Main(string[] args)
        {    
            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}");
            }
        }
    }
}

Run the program and check the Azure portal.

Select the name of your queue in the namespace Overview window to display queue Essentials.

The Active message count value for the queue is now 10. Each time you run this sender app without retrieving the messages, this value increases by 10.

The current size of the queue increments the CURRENT value in Essentials each time the app adds messages to the queue.

The next section describes how to retrieve these messages.

Receive messages from the queue

To receive the messages you sent, create another Console App (.NET Core) application. Install the Microsoft.Azure.ServiceBus NuGet package, as you did for the 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;
   using System.Text;
   using System.Threading;
   using System.Threading.Tasks;
   using Microsoft.Azure.ServiceBus;
   

2. In the Program class, declare the following variables:

   const string ServiceBusConnectionString = "<your_connection_string>";
   const string QueueName = "<your_queue_name>";
   static IQueueClient queueClient;
   

   Enter your connection string for the namespace as the ServiceBusConnectionString variable. Enter your queue name.

3. Replace the Main() method with the following code:

   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();
   }
   

4. Directly after the MainAsync() method, add the following method, which 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);
   }
   

5. 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.
   }
   

6. 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;
   }
   

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;
        }
    }
}

Run the program, and check the portal again. The Active message count and CURRENT values are now 0.

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

Next steps

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