How to Send & Read Messages with Azure Service Bus Queues in Azure Functions

Select the HTTP trigger template set the Authorization level as Anonymous and click on Create.

That's it. We have created our first Azure function. By default the name of the function is Function1.cs so now change it to "SendMessage".

Azure Functions has Triggers and Bindings. Triggers are the ones due to which function code starts executing forex. In the case of an HTTP trigger whenever you make an HTTP request by hitting the function URL the specific function will start its execution. The Azure function must have only one trigger. Bindings are the direction of data coming in or going out from the function. We have In, out, and both types of bindings.

So for our application, we are creating an HTTP Trigger function that takes data and sends it into the Queue. So to send data to the queue we are using an Output binding. To connect with the queue we need a connection string. So let's open the Service bus resource in portal -> Shared Access Policy -> Copy the Primary Connection String under RootManagedSharedAccessKey

First, install the below NuGet package.

Open the local.settings.json file in our function app add a key called "AzureWebJobsServiceBus" and paste the connection string of our Service bus resource.

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet",
        "AzureWebJobsServiceBus": "<replace your RootManageSharedAccessKey here>"
    }
}

Now add the below code to send a message to the queue using output bindings.

using System.IO;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.ServiceBus;
using Microsoft.Extensions.Logging;

namespace AzServiceBusDemo
{
    public static class SendMessage
    {
        [FunctionName("SendMessage")]
        [return: ServiceBus("az-queue", EntityType.Queue)]
        public static async Task<string> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("SendMessage function requested");
            string body = string.Empty;
            using (var reader = new StreamReader(req.Body, Encoding.UTF8))
            {
                body = await reader.ReadToEndAsync();
                log.LogInformation($"Message body : {body}");
            }
            log.LogInformation($"SendMessage processed.");
            return body;
        }
    }
}

• From lines 21-28, we are just getting data from the request body & assigning it to a local variable. After that, we are just returning it from function.
• In line 15, since we are using C# for creating a function, we can use ServiceBusAttribute to specify the output bindings. For the attribute constructor i.e. ServiceBus() we just need to pass queue name and type of entity to bind.

Now run the SendMessage function.

To test the function open Postman and hit the About function URL.

Since we logged our request body, we can see the content.

Open queue "az-queue" and we can see the Active message count is now showing as 1.

To check the message content in the queue you can click on Service Bus Explorer(preview) in the left sidebar and then click on Peek and finally click on the message to see the content.

Create a Service Bus Queue trigger Azure function to read a message from Queue

Now the final step is to read a message from the queue i.e. "az-queue". Right-click on the project and click on project -> Click on Add -> Select New Azure Function. Select the Azure function give it a name and click on Add button.

Now select Service Bus Queue Trigger specify the queue name and click on the Add button.

That's it our Service Bus trigger function is created.

using Microsoft.Azure.WebJobs;
using Microsoft.Extensions.Logging;
namespace AzServiceBusDemo
{
    public static class ReadMessageFromQueue
    {
        [FunctionName("ReadMessageFromQueue")]
        public static void Run([ServiceBusTrigger("az-queue")]string myQueueItem, ILogger log)
        {
            log.LogInformation($"C# ServiceBus queue trigger function processed message: {myQueueItem}");
        }
    }
}

Now run our function app. Since we already have one active message in our queue, as soon as the function starts it will read a message from the queue as shown below.

So in this way, we can use Azure functions to send and read messages from Azure Service Bus Queues.

Conclusion

In this article, we have created a new Azure Service Bus instance and added a new queue from the portal. Also, we have created the HTTP trigger Azure function to send messages into the Queue and Service Bus Queue trigger function to read messages from a queue.I really hope that you enjoyed this article, share it with friends and please do not hesitate to send me your thoughts or comments.

Stay tuned for more articles on Azure Functions.

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Happy Coding!