How to Run Background Tasks in ASP.NET Core with Hosted Services

Background tasks are particularly useful in microservices architectures, where you often need to implement a messaging service like RabbitMQ to listen for and consume messages from a message queue.

Start by creating a new ASP.NET Core web application, then create a new class named HelloWorldHostedService.

This class will implement the IHostedService interface.

public class HelloWorldHostedService : IHostedService
{
    private Timer _timer;

    // Run the logic when the service starts
    public Task StartAsync(CancellationToken cancellationToken)
    {
        // Register the background task using a timer
        RegisterTimerTask();
        return Task.CompletedTask;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        Debug.WriteLine("Stopping task...");
        return Task.CompletedTask;
    }

    private void RegisterTimerTask()
    {
        // Call HelloWorld every 5 seconds in the background
        _timer = new Timer(HelloWorld, null, 0, 5000);
    }

    void HelloWorld(object state)
    {
        Debug.WriteLine($"{DateTime.Now}");
        Debug.WriteLine("Hello World!");
        Debug.WriteLine("This is a hosted service");
    }
}

The IHostedService interface requires you to implement StartAsync() and StopAsync() methods. In our example, we use a timer to invoke the HelloWorld() method every 5 seconds.

• In the StartAsync() method, we register the timer by calling the RegisterTimerTask() method.
• In the StopAsync() method, we simply log a message when the service stops.

Now, open your Startup.cs file and register the hosted service:

// Register the hosted service
services.AddHostedService<HelloWorldHostedService>();

Run your application.

You should see the background task running in the Output window of Visual Studio, printing the "Hello World" message every 5 seconds.

Alternatively, you can use the BackgroundService class, which is a simplified base class for running background tasks in ASP.NET Core.

public class HelloWorldBackgroundService : BackgroundService
{
    protected async override Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            Debug.WriteLine("Background service running!! Hello!");
            await Task.Delay(8000, stoppingToken);
        }
    }
}

Similar to the previous approach, you need to register the background service in your Startup.cs file:

// Register the background service
services.AddHostedService<HelloWorldBackgroundService>();

That's all there is to creating a simple background task in an ASP.NET Core application. Whether you use IHostedService or BackgroundService, the process is straightforward:

1. Create a class that implements IHostedService or BackgroundService.
2. Implement the logic for the background task.
3. Register the service in your Startup.cs file.