重写 IHostedService 以在所有任务完成后停止

我有一个应用程序，通常应该是一个简单的控制台应用程序，可以编程为 Windows 任务计划程序不时调用的计划任务。

该程序应该在两个数据库上启动一些更新，每个数据库一项服务。说ContosoDatabase应由ContosoService.

最后它被编写为 .NET Core 应用程序，使用：也许不是最好的选择, the IHostedServices 作为服务的基础，如下所示：

public class ContosoService : IHostedService {
    private readonly ILogger<ContosoService> _log;
    private readonly IContosoRepository _repository;
    
    private Task executingTask;

    public ContosoService(
        ILogger<ContosoService> log,
        IContosoRepository repository,
        string mode) {
        _log = log;
        _repository = repository;
    }

    public Task StartAsync(CancellationToken cancellationToken) {
        _log.LogInformation(">>> {serviceName} started <<<", nameof(ContosoService));
        executingTask = ExcecuteAsync(cancellationToken);

        // If the task is completed then return it, 
        // this should bubble cancellation and failure to the caller
        if (executingTask.IsCompleted)
            return executingTask;

        // Otherwise it's running
        // >> don't want it to run!
        // >> it should end after all task finished!
        return Task.CompletedTask;
    }

    private async Task<bool> ExcecuteAsync(CancellationToken cancellationToken) {
        var myUsers = _repository.GetMyUsers();

        if (myUsers == null || myUsers.Count() == 0) {
            _log.LogWarning("{serviceName} has any entry to process, will stop", this.GetType().Name);
            return false;
        }
        else {
            // on mets à jour la liste des employés Agresso obtenue
            await _repository.UpdateUsersAsync(myUsers);
        }

        _log.LogInformation(">>> {serviceName} finished its tasks <<<", nameof(ContosoService));
        return true;
    }

    public Task StopAsync(CancellationToken cancellationToken) {
        _log.LogInformation(">>> {serviceName} stopped <<<", nameof(ContosoService));
        return Task.CompletedTask;
    }
}

我从 main 中这样称呼它：

public static void Main(string[] args)
{
    try {
        CreateHostBuilder(args).Build().Run();
    }
    catch (Exception ex) {
        Log.Fatal(ex, ">>> the application could not start <<<");
    }
}

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host
    .CreateDefaultBuilder(args)
    .ConfigureServices((hostContext, services) => {
        var config = hostContext.Configuration;
        
        if (args.Contains("Alonso")) {
            services
            .AddHostedService(provider =>
                new AlonsoService(
                    provider.GetService<ILogger<AlonsoService>>(),
                    provider.GetService<IAlonsoRepository>()));
        }

        // if there also Cedig in the list, they can be run in parallel
        if (args.Contains("Contoso")) {
            services
            .AddHostedService(provider =>
                new ContosoService(
                    provider.GetService<ILogger<ContosoService>>(),
                    provider.GetService<IContosoRepository>()));
        }
    });

现在的问题肯定是，一旦所有更新完成，应用程序就不会停止。

有没有办法快速重写应用程序，使其在第二个服务完成其任务后停止？

我试图把Environment.Exit(0);在最后

public static void Main(string[] args) {
    try {
        CreateHostBuilder(filteredArgs.ToArray()).Build().Run();                
    }
    catch (Exception ex) {
        //Log....
    }

    Environment.Exit(0); // here
}

但它似乎没有帮助：所有任务完成后应用程序仍在运行。

按照@Maxim的建议，我发现了这个肮脏但有效的解决方法，通过注入IHostApplicationLifetime和lastService布尔值：

public ConsosoService(
    IHostApplicationLifetime hostApplicationLifetime,
    // ...
    bool lastService) 
{ ... }

public async Task StartAsync(CancellationToken cancellationToken)
{
    // do the job

    if (_lastService)
        _hostApplicationLifetime.StopApplication(); 
    // stops the application and cancel/stops other services as well
}