How do you implement background tasks in .NET Core?

Create a class inheriting from BackgroundService and override ExecuteAsync(). Register it using AddHostedService in Program.cs.

Using BackgroundService in ASP.NET Core | FullStackPrep.Dev

Q: What is BackgroundService in ASP.NET Core?

BackgroundService is a base class for implementing long-running background tasks that run independently of user requests in ASP.NET Core.

💡 Concept Name

BackgroundService in ASP.NET Core

📘 Quick Intro

BackgroundService is an abstract base class in ASP.NET Core that allows you to run long-running tasks on a separate thread, independent of HTTP requests.

🧠 Analogy / Short Story

Imagine a restaurant that needs to bake bread every morning. Rather than tying up the waiters, a dedicated baker (background service) quietly works behind the scenes, making fresh bread for the day ahead — always running, but not interrupting the main business.

🔧 Technical Explanation

🧵 Inherits from BackgroundService (from Microsoft.Extensions.Hosting).
🔁 Executes background logic inside the overridden ExecuteAsync() method.
🛠 Can be registered in Startup.cs or Program.cs using services.AddHostedService<T>().
⏱ Suitable for polling, scheduled jobs, messaging, cleanup tasks, etc.
❌ Should not use for UI-based operations or logic tied directly to HTTP requests.

🎯 Purpose & Use Case

✅ Periodic data cleanup or archiving.
✅ Polling external APIs.
✅ Queue processing (e.g., background emails or SMS sending).
✅ Background health monitoring.

💻 Real Code Example

Simple background service that logs a message every 10 seconds:

public class WorkerService : BackgroundService
{
    private readonly ILogger<WorkerService> _logger;

    public WorkerService(ILogger<WorkerService> logger)
    {
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            _logger.LogInformation("Background task running at: {time}", DateTimeOffset.Now);
            await Task.Delay(10000, stoppingToken);
        }
    }
}

// Register in Program.cs
builder.Services.AddHostedService<WorkerService>();

❓ Interview Q&A

Q1: What is BackgroundService?
A: A base class for implementing long-running background tasks in ASP.NET Core.

Q2: Which method must you override in BackgroundService?
A: ExecuteAsync().

Q3: Where is a BackgroundService registered?
A: In the DI container using AddHostedService<T>().

Q4: Is it tied to HTTP requests?
A: No, it runs independently.

Q5: Can BackgroundService be used for scheduled jobs?
A: Yes, using Task.Delay() or third-party schedulers like Quartz.NET.

📝 MCQs

Q1. What is BackgroundService in ASP.NET Core?

A controller
A middleware
A base class for long-running background tasks
A static method

Q2. Which method is overridden in BackgroundService?

Main
Configure
Execute
ExecuteAsync

Q3. How do you register a BackgroundService?

app.UseBackground()
AddSingleton()
services.AddHostedService
AddController()

Q4. Does BackgroundService run on a separate thread?

No
Yes
Only in dev mode
Only when idle

Q5. Is BackgroundService tied to user requests?

Yes
No
Only GET requests
Only POST requests

💡 Bonus Insight

For more advanced scheduling, consider integrating Quartz.NET or Hangfire for cron-based or queue-backed background jobs. Also, avoid blocking operations inside ExecuteAsync to keep the app responsive.

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Using BackgroundService in ASP.NET Core