In ASP.NET Core, you can implement background tasks using the BackgroundService class or the IHostedService interface. The BackgroundService class provides a base class for implementing long-running background tasks. You can override the ExecuteAsync method to define the logic of your background task. The IHostedService interface allows you to implement background services that start and stop with the application. Implementing the StartAsync and StopAsync methods in the IHostedService interface gives you more control over the lifecycle of the background task.