รูปแบบ CancellationToken และการยกเลิกแบบร่วมมือกัน

การยกเลิกแบบร่วมมือ

การยกเลิกโดยผู้เรียก

using System;
using System.Threading;
using System.Threading.Tasks;

public class Program
{
  static async Task WorkAsync(CancellationToken ct)
  {
    // Poll occasionally; throw to end cooperatively
    for (int i = 0; i < 5; i++)
    {
      ct.ThrowIfCancellationRequested();
      Console.WriteLine("Step " + i);
      await Task.Delay(100, ct); // pass token to async API
    }
  }

  public static void Main(string[] args)
  {
    var cts = new CancellationTokenSource();
    Task t = WorkAsync(cts.Token);

    // Cancel after a short delay (simulated user action)
    Thread.Sleep(180);
    cts.Cancel();

    try
    {
      t.GetAwaiter().GetResult();
    }
    catch (OperationCanceledException)
    {
      Console.WriteLine("Canceled!");
    }
  }
}

การส่งต่อโทเค็น

using System;
using System.Threading;
using System.Threading.Tasks;

public class Program
{
  static async Task<string> FetchAsync(CancellationToken ct)
  {
    await Task.Delay(80, ct); // pretend I/O
    ct.ThrowIfCancellationRequested();
    return "data";
  }

  static async Task<string> ProcessAsync(CancellationToken ct)
  {
    string raw = await FetchAsync(ct); // forward token
    await Task.Delay(80, ct);
    return raw.ToUpperInvariant();
  }

  public static void Main(string[] args)
  {
    var cts = new CancellationTokenSource();
    Task<string> job = ProcessAsync(cts.Token);
    cts.CancelAfter(100); // schedule a cancellation
    try
    {
      Console.WriteLine(job.GetAwaiter().GetResult());
    }
    catch (OperationCanceledException)
    {
      Console.WriteLine("Pipeline canceled");
    }
  }
}

การล้างทรัพยากรด้วย token.Register

using System;
using System.Threading;
using System.Threading.Tasks;

public class Program
{
  static async Task UseRegistrationAsync(CancellationToken ct)
  {
    using (ct.Register(() => Console.WriteLine("Cleanup: releasing temp resources")))
    {
      for (int i = 0; i < 3; i++)
      {
        ct.ThrowIfCancellationRequested();
        await Task.Delay(120, ct);
        Console.WriteLine("Tick " + i);
      }
    }
  }

  public static void Main(string[] args)
  {
    var cts = new CancellationTokenSource();
    Task t = UseRegistrationAsync(cts.Token);
    Thread.Sleep(150);
    cts.Cancel();
    try { t.GetAwaiter().GetResult(); }
    catch (OperationCanceledException) { Console.WriteLine("Canceled with cleanup"); }
  }
}

แหล่งต้นทางที่เชื่อมโยง

using System;
using System.Threading;
using System.Threading.Tasks;

public class Program
{
  static async Task WorkAsync(CancellationToken ct)
  {
    await Task.Delay(500, ct);
    Console.WriteLine("Finished work");
  }

  public static void Main(string[] args)
  {
    var parent = new CancellationTokenSource();
    var timeout = new CancellationTokenSource();
    timeout.CancelAfter(200);

    // Link both sources: cancel if parent OR timeout requests
    var linked = CancellationTokenSource.CreateLinkedTokenSource(parent.Token, timeout.Token);

    Task t = WorkAsync(linked.Token);
    try { t.GetAwaiter().GetResult(); }
    catch (OperationCanceledException) { Console.WriteLine("Canceled by parent/timeout"); }
    finally { linked.Dispose(); parent.Dispose(); timeout.Dispose(); }
  }
}

แนวทางปฏิบัติที่ดี

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