ASP.NET Lifetime Event Handler

LifetimeEventsHostedService.cs

internal class LifetimeEventsHostedService : IHostedService
    {
        private readonly ILogger<LifetimeEventsHostedService> _logger;
        private readonly IHostApplicationLifetime _appLifetime;
        private readonly TelemetryClient _telemtryClient;

        public LifetimeEventsHostedService(
            ILogger<LifetimeEventsHostedService> logger,
            IHostApplicationLifetime appLifetime,
            TelemetryClient telemtryClient)
        {
            _logger = logger;
            _appLifetime = appLifetime;
            _telemtryClient = telemtryClient;
        }

        public Task StartAsync(CancellationToken cancellationToken)
        {
            _appLifetime.ApplicationStarted.Register(OnStarted);
            _appLifetime.ApplicationStopping.Register(OnStopping);
            _appLifetime.ApplicationStopped.Register(OnStopped);

            return Task.CompletedTask;
        }

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

        private void OnStarted()
        {
        }

        private void OnStopping()
        {
            _logger.LogInformation("OnStopping has been called.");
            _telemtryClient.Flush();
        }
              
        private void OnStopped()
        {
        }
    }