using System; using UIKit; using System.Threading.Tasks; namespace MyApp { class BackgroundTaskExample { public async void StartBackgroundTask() { var taskId = UIApplication.SharedApplication.BeginBackgroundTask(() => { // Handle any cleanup tasks here UIApplication.SharedApplication.EndBackgroundTask(taskId); }); // Do some long-running work here in a separate async method await LongRunningTask(); // Once the long-running work is done, end the background task UIApplication.SharedApplication.EndBackgroundTask(taskId); } private async Task LongRunningTask() { // Perform some long-running operation here await Task.Delay(5000); } } }In this example, the `StartBackgroundTask` method begins a new background task using the `BeginBackgroundTask` method. The task ID is stored in a variable so it can be passed to the `EndBackgroundTask` method later on. Inside the background task, a separate async method `LongRunningTask` is called that performs some long-running operation using the `Task.Delay` method. Once the long-running operation is complete, the `EndBackgroundTask` method is called to signal to the system that the task is finished. The package library for this code example is likely the `Xamarin.iOS` library, which provides C# bindings for iOS APIs.