ASP.NET Async Generic Host Example

await new HostBuilder()
    .ConfigureServices((hostContext, services) =>
    {
        services.AddHostedService<CountingService>();
    })
    .UseConsoleLifetime()
    .ConfigureLogging(logging =>
    {
        logging.ClearProviders();
        logging.AddConsole();
        logging.AddFilter((provider, category, logLevel) =>
        {
            return !category.Contains("Microsoft");
        });
    })
    .Build().RunAsync();

public class CountingService : IHostedService, IDisposable
{
    CancellationTokenSource _stoppingCts = new CancellationTokenSource();

    Task _executingTask;

    readonly ILogger _log;

    public CountingService(ILogger<CountingService> logger)
    {
        _log = logger;
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _executingTask = ExecuteAsync(_stoppingCts.Token);

        return _executingTask.IsCompleted ? _executingTask : Task.CompletedTask;
    }

    async Task ExecuteAsync(CancellationToken cancellationToken)
    {
        var count = 0;
        do
        {
            _log.LogDebug(count.ToString());
            count++;
            await Task.Delay(1000, cancellationToken);
        } while (!cancellationToken.IsCancellationRequested);
    }

    public async Task StopAsync(CancellationToken cancellationToken)
    {
        if (_executingTask == null)
            return;

        try
        {
            _stoppingCts.Cancel();
        }
        finally
        {
            await Task.WhenAny(_executingTask, Task.Delay(Timeout.Infinite, cancellationToken));
        }
    }

    public void Dispose() => _stoppingCts.Cancel();
}

// Example 2 (https://github.com/dodyg/practical-aspnetcore/blob/net8.0/projects/generic-host/generic-host-ihostapplicationlifetime/Program.cs)
await new HostBuilder()
    .ConfigureServices((hostContext, services) =>
    {
        services.AddHostedService<HelloWorldService>();
    })
    .ConfigureLogging(logging =>
    {
        logging.ClearProviders();
        logging.AddConsole();
        logging.AddFilter((provider, category, logLevel) =>
                {
          return !category.Contains("Microsoft");
      });
    })
    .Build().RunAsync();

public class HelloWorldService : IHostedService
{
    readonly IHostApplicationLifetime _lifetime;
    readonly ILogger _log;

    public HelloWorldService(IHostApplicationLifetime lifetime, ILogger<HelloWorldService> logger)
    {
        _log = logger;
        _lifetime = lifetime;
        _lifetime.ApplicationStarted.Register(OnStarted);
        _lifetime.ApplicationStopping.Register(OnStopping);
        _lifetime.ApplicationStopped.Register(OnStopped);
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        _log.LogDebug("StartAsync");
        return Task.CompletedTask;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        _log.LogDebug("StopAsync");
        return Task.CompletedTask;
    }

    void OnStarted()
    {
        _log.LogDebug("OnStarted");
    }

    void OnStopping()
    {
        _log.LogDebug("OnStopping");
    }

    void OnStopped()
    {
        _log.LogDebug("OnStopped");
    }

}