What is Azure Queue Storage?

Azure Queue Storage is a service for storing large numbers of messages. You access messages from anywhere in the world via authenticated calls using HTTP or HTTPS. A queue message can be up to 64 KB in size. A queue may contain millions of messages, up to the total capacity limit of a storage account. Queues are commonly used to create a backlog of work to process asynchronously.

Queue Storage Concepts

Azure Queue Storage implements cloud-based queues to enable communication between components of a distributed application. Each queue maintains a list of messages that can be added by a sender component and processed by a receiver component. Here are the components of the Queue Storage:

URL format: Queues are addressable using the following URL format:

https://<storage account>.queue.core.windows.net/<queue>

Storage account: All access to Azure Storage is done through a storage account.
Queue: A queue contains a set of messages. The queue name must be all lowercase.
Message: A message, in any format, of up to 64 KB. The maximum time-to-live allowed is seven days it can be modified to any positive number, or -1 indicating that the message doesn't expire. If this parameter is omitted, the default time-to-live is seven days.

Here is a screenshot summarizing the components included in the Azure Queue service:

How to Access the Queue Storage using .NET

In the following steps, we are going to build a .NET console application to read IoT messages stored in the Queue Storage through Azure IoT Hub. For this tutorial, we are going to use the Visual Studio 2022 community version and the application will be created using .NET 6.

Step 1: Creating a .NET 6 Console Application

Open VS2022, then from the top menu click on File
From the menu, select New then Project
Select Console App from the project templates, as per the following screenshot:

Use "ReadFromAzureQueue" as the project name, then click Next to create the project. Make sure you select .NET6 which is the version used in this tutorial.

Here is a screenshot showing what the final outcome should look like:

Read data from Azure Queue - Console App

Step 2: Installing Package “Azure.Storage.Queues”

Open NuGet package manager
Search online for package "Azure.Storage.Queues". We will install version "12.8.0".
Click install to install the package and its dependencies. After that, you should be able to see the installed package under packages in the console application. The following screenshot showing the package installed under packages in our console application:

Step 3: Retrieve the ConnectionString from Azure

In order to query the queue storage we must be authenticated and authorized to access the assets. Otherwise, Azure will not allow us to access the storage.

Login to the Azure Portal
Retrieve the storage account
In the Settings section of the storage account overview, select Access keys. The account access keys appear, as well as the complete connection string for each key.
Find the Connection string value under key1, and click the Copy button to copy the connection string. We will use this connection string to connect to the Queue in the next step.

Step 4: Retrieving Message from Azure Queue using .NET API

In this step, we are going to use the API from the installed package "Azure.Storage.Queues" to retrieve the messages. Copy the following code snippet and paste it into the file "Program.cs":

static async Task Main(string[] args)
    {
        string connectionString = "Put Here The Connection String We Copied In Step 3";

        QueueClient queue = new QueueClient(connectionString, "UseTheQueueNameHere");

        string value = await RetrieveNextMessageAsync(queue);
        Console.WriteLine($"Received: {value}");

        Console.Write("Press Enter...");
        Console.ReadLine();
    }

static async Task<string> RetrieveNextMessageAsync(QueueClient theQueue)
    {
        if (await theQueue.ExistsAsync())
        {
            QueueProperties properties = await theQueue.GetPropertiesAsync();

            if (properties.ApproximateMessagesCount > 0)
            {
                QueueMessage[] retrievedMessage = await theQueue.ReceiveMessagesAsync(1);
                string encodedString = retrievedMessage[0].Body.ToString();

                byte[] data = Convert.FromBase64String(encodedString);
                string decodedString = Encoding.UTF8.GetString(data);
                return decodedString;
            }
            return string.Empty;
        }
        return string.Empty;
    }

Make sure you replace the connection string along with the correct queue name found in the code with the right parameters from your Azure Storage.

Run the code and you should be able to see the messages printed in the console window.

Tutorial: How to Read and Decode Messages from Azure Queue