RabbitMQ Fanout Exchange in C# to Publish or Consume Messages

In rabbitmq, Fanout Exchange will route messages to all of the queues that are bound to it.

 

The fanout exchange is useful when we want to publish a common message to all the queues that are bound with a particular exchange and in the fanout exchange, the routing key is ignored.

 

For example, if the company has updated some guidelines and you want to push those guidelines to all the branches that time you can use fanout exchange.

 

Generally, in rabbitmq when the producer creates a message that will not directly send to the queue, instead first the message will be sent to exchanges, then after that, a routing agent reads and sends it to the appropriate queue with help of header attributes, bindings and routing keys.

 

In rabbitmq, we have different types of exchanges available are

 

  • Direct
  • Fanout
  • Topic
  • Headers

To know more about exchanges in rabbitmq, check this RabbitMQ Exchanges.

 

Following is the pictorial representation of message flow in the rabbit fanout exchange.

 

RabbitMQ Fanout Exchange Process Flow Diagram

 

Now, we will learn how to use Fanout Exchange to push and read messages from rabbitmq in c# or .net application with examples.

C# Create RequestRabbitMQ Application

Let’s create a simple console application with the Name “RequestRabbitMQ” as shown below to publish messages to the rabbitmq queue using fanout exchange in c#.

 

C# Create Application to Publish Messages to RabbitMQ

 

After creating an application, now we will add the “RabbitMQ.Client” NuGet package in our c# application to communicate with rabbitmq server to publish or consume messages from queues in rabbitmq.

Add RabbitMQ.Client NuGet Package

In c#, we can publish or consume messages from rabbitmq by using RabbitMQ.Client NuGet package for that, right-click on your application and select Manage NuGet Packages as shown below.

 

C# Add RabbitMQ.Client Nuget Package Reference to Application

 

Now search for RabbitMQ.Client package and install it in your application as shown below.

 

C# Adding RabbitMQ.Client NuGet Package Reference

 

Following is another way to install RabbitMQ.Client package by using Package Manager Console as shown below by entering the following command.

 

Command to install - Install-Package RabbitMQ.Client -Version 5.1.0 

 

C# Add RabbitMQ.Client Nuget Package Reference from Package Manager Console

 

Before we start writing a code in c# to publish messages to rabbitmq, we will create a fanout exchange, queue and will bind a queue to exchange using the web admin console.

RabbitMQ Create Fanout Exchange

To create an exchange in rabbitmq web management portal, open http://localhost:15672/#/exchanges url and then go to Add a new exchange panel and enter details as shown below by selecting Type as “fanout” and click on Add exchange button to create an exchange (fanout.exchange).

 

RabbitMQ Create Fanout Exchange

 

After creating an exchange (fanout.exchange), next, we will create 4 queues (Mumbai, Hyderabad, Bangalore, and Chennai) and bind them to the same exchange (fanout.exchange) in the web management portal.

RabbitMQ Create a Queue

To create a queue in rabbitmq web management portal, open http://localhost:15672/#/queues url and then go to Add a new queue panel and enter details as shown below, and click on Add queue button to create a queue (Mumbai).

 

Create a Queue in RabbitMQ Web Management Portal

 

Similar way, add the remaining three queues (Bangalore, Chennai, Hyderabad) in rabbitmq as shown below.

 

RabbitMQ Fanout Exchange Queues List

 

After adding all the queues, next we will bind all the queues to “fanout.exchange” in rabbitmq web admin console.

RabbitMQ Bind Queue to Exchange

To bind a queue with an exchange, click on the queue (Bangalore) name, then the Bindings panel will expand and enter details like exchange name as “fanout.exchange” and click on the Bind button as shown below.

 

RabbitMQ Fanout Exchange Bind Queues

 

After binding a queue (Bangalore) to exchange (fanout.exchange), the binding will be as shown below.

 

RabbitMQ Fanout Exchange Queue Binding Details

 

Same way, bind the remaining queues (Chennai, Hyderabad, Mumbai) also to an exchange (fanout.exchange) in rabbitmq web admin console.

 

After the completion of binding queues (Bangalore, Chennai, Hyderabad, Mumbai) to an exchange (fanout.exchange), now we will publish messages from the c# application to rabbitmq queues using RabbitMQ.Client service.

C# Publish Messages to RabbitMQ

To publish messages to the rabbitmq queue, add a class with the name “Fanoutmessages.cs” in your application as shown below.

 

C# Add Class to Publish Messages to RabbitMQ using Fanout Exchange

 

Now, open the Fanoutmessages.cs class file and write the code as shown below.

Fanoutmessages.cs

using System;
using RabbitMQ.Client;
using System.Text;

namespace RequestRabbitMQ
{
   public class Fanoutmessages
   {
     private const string UName = "guest";
     private const string PWD = "guest";
     private const string HName = "localhost";

     public void SendMessage()
     {
       //Main entry point to the RabbitMQ .NET AMQP client
       var connectionFactory = new ConnectionFactory()
       {
         UserName = UName,
         Password = PWD,
         HostName = HName
       };
       var connection = connectionFactory.CreateConnection();
       var model = connection.CreateModel();
       var properties = model.CreateBasicProperties();
       properties.Persistent = false;
       byte[] messagebuffer = Encoding.Default.GetBytes("Message is of fanout Exchange type");
       model.BasicPublish("fanout.exchange", "", properties, messagebuffer);
       Console.WriteLine("Message Sent From : fanout.exchange");
       Console.WriteLine("Routing Key : Routing key is not required for fanout exchange");
       Console.WriteLine("Message Sent");
     }
   }
}

If you observe the above code, to establish a connection with rabbitmq server we are passing the required credentials along with the HostName to ConnectionFactory() method. After that, we are publishing a message (Message is of fanout Exchange type) to the queue by passing required parameters like an exchange, routing key, properties, and message to the BasicPublish method.

 

Now open Program.cs class file and write a code in the Main method to call Fanoutmessages.cs class to get messages from rabbitmq.

Program.cs

Following is the code which we need to write in Program.cs class file Main method to publish messages to rabbitmq server.

 

using System;

namespace RequestRabbitMQ
{
   class Program
   {
      static void Main(string[] args)
      {
         Fanoutmessages fanoutmessages = new Fanoutmessages();
         fanoutmessages.SendMessage();
         Console.ReadLine();
      }
   }
}

When we execute the above c# program, we will get the result as shown below.

 

C# Publish Message to RabbitMQ using Fanout Exchange Example Result

 

After executing the above program, if we check the queues (Bangalore, Chennai, Hyderabad, Mumbai) status details in rabbitmq web management portal, the Ready column is having 1 like as shown below which means the message was published successfully to all the queues of fanout exchange.

 

RabbitMQ Fanout Exchange Queues After Publishing Messages

 

After creating an application, now add “RabbitMQ.Client” NuGet package reference to your application like as we did in publishing application to communicate with rabbitmq server.

C# Consume Messages from RabbitMQ

After installing RabbitMQ.Client, next add a class with the name “MessageReceiver.cs” in your application as shown below to read or get messages from queues in rabbitmq.

 

C# Console Application Add New Class File to Read Messages from RabbitMQ

 

Now, open MessageReceiver.cs class file and write the code as shown below.

MessageReceiver.cs

using System;
using System.Text;
using RabbitMQ.Client;

namespace RabbitMQConsumer
{
   public class MessageReceiver : DefaultBasicConsumer
   {
     private readonly IModel _channel;
     public MessageReceiver(IModel channel)
     {
        _channel = channel;
     }
     public override void HandleBasicDeliver(string consumerTag, ulong deliveryTag, bool redelivered, string exchange, string routingKey, IBasicProperties properties, byte[] body)
     {
        Console.WriteLine($"Consuming fanout Message");
        Console.WriteLine(string.Concat("Message received from the exchange ", exchange));
        Console.WriteLine(string.Concat("Consumer tag: ", consumerTag));
        Console.WriteLine(string.Concat("Delivery tag: ", deliveryTag));
        Console.WriteLine(string.Concat("Routing tag: ", routingKey));
        Console.WriteLine(string.Concat("Message: ", Encoding.UTF8.GetString(body)));
        _channel.BasicAck(deliveryTag, false);
     }
   }
}

If you observe the above code, we created a MessageReceiver class and it’s inheriting from DefaultBasicConsumer class of RabbitMQ.Client service and we implemented a HandleBasicDeliver method by overriding it to receive a message body.

 

Now open Program.cs class file and write a code in the Main method to call MessageReceiver.cs class to get messages from rabbitmq.

Program.cs

Following is the code which we need to write in Program.cs class file Main method to receive data from rabbitmq server.

 

using System;
using RabbitMQ.Client;

namespace RabbitMQConsumer
{
   class Program
   {
      private const string UName = "guest";
      private const string Pwd = "guest";
      private const string HName = "localhost";

      static void Main(string[] args)
      {
         ConnectionFactory connectionFactory = new ConnectionFactory
         {
           HostName = HName,
           UserName = UName,
           Password = Pwd,
         };
         var connection = connectionFactory.CreateConnection();
         var channel = connection.CreateModel();
         // accept only one unack-ed message at a time
         // uint prefetchSize, ushort prefetchCount, bool global
         channel.BasicQos(0, 1, false);
         MessageReceiver messageReceiver = new MessageReceiver(channel);
         channel.BasicConsume("Mumbai", false, messageReceiver);
         Console.ReadLine();
      }
   }
}

If you observe the above example, to establish a connection with rabbitmq server we are passing the required credentials along with the HostName to ConnectionFactory() method. After that, we created a connection and channel by calling the “CreateConnection” and “CreateModel” methods and we set a prefetchCount to 1, so that it tells RabbitMQ not to give more than one message at a time to the worker.

 

Next, we created an instance of MessageReceiver class and passed IModel (channel) to it, in the final step we called the “BasicConsume” method and passed the queue name to it “Mumbai” along with we have set autoAck to false and passed the messageReceiver instance to it. 

 

Here, prefetchCount is used to tell RabbitMQ not to give more than one message at a time to the worker. Or, in other words, don't dispatch a new message to a worker until it has been processed and acknowledged the previous one. Instead, it will dispatch to the next worker that is not still busy. 

 

When we execute our application, we will get messages from the queue (Mumbai) as shown below.

 

C# Consume Messages from RabbitMQ using Fanout Exchange Example Result

 

After reading the messages from the Mumbai queue, the following is the status of a queue in the web management portal.

 

RabbitMQ Fanout Exchange After Reading a Message from Queue

Same way, we can read messages from Bangalore or Chennai, or Hyderabad queues based on our requirements.

 

This is how we can use fanout exchange in rabbitmq to publish messages to all the queues which are bound with an exchange. 

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