问停止子系统:单CancellationToken与停止方法

EN

 public abstract class BackgroundService : IHostedService, IDisposable
  {
    private readonly CancellationTokenSource _stoppingCts = new CancellationTokenSource();
    private Task _executingTask;

    /// <summary>
    /// This method is called when the <see cref="T:Microsoft.Extensions.Hosting.IHostedService" /> starts. The implementation should return a task that represents
    /// the lifetime of the long running operation(s) being performed.
    /// </summary>
    /// <param name="stoppingToken">Triggered when <see cref="M:Microsoft.Extensions.Hosting.IHostedService.StopAsync(System.Threading.CancellationToken)" /> is called.</param>
    /// <returns>A <see cref="T:System.Threading.Tasks.Task" /> that represents the long running operations.</returns>
    protected abstract Task ExecuteAsync(CancellationToken stoppingToken);

    /// <summary>
    /// Triggered when the application host is ready to start the service.
    /// </summary>
    /// <param name="cancellationToken">Indicates that the start process has been aborted.</param>
    public virtual Task StartAsync(CancellationToken cancellationToken)
    {
      this._executingTask = this.ExecuteAsync(this._stoppingCts.Token);
      if (this._executingTask.IsCompleted)
        return this._executingTask;
      return Task.CompletedTask;
    }

    /// <summary>
    /// Triggered when the application host is performing a graceful shutdown.
    /// </summary>
    /// <param name="cancellationToken">Indicates that the shutdown process should no longer be graceful.</param>
    public virtual async Task StopAsync(CancellationToken cancellationToken)
    {
      if (this._executingTask == null)
        return;
      try
      {
        this._stoppingCts.Cancel();
      }
      finally
      {
        Task task = await Task.WhenAny(this._executingTask, Task.Delay(-1, cancellationToken));
      }
    }

    public virtual void Dispose()
    {
      this._stoppingCts.Cancel();
    }

public class LongRunningService
{
    public Task RunAsync(CancellationToken token)
    {
        return Task.Factory.StartNew(() =>
            {
                // here goes something long running
                while (!token.IsCancellationRequested)
                {

                }
            },
            TaskCreationOptions.LongRunning);
    }
}