Task/ValueTask وآلة الحالة غير المتزامنة (مفاهيم)

النموذج الذهني

أساسيات الطريقة غير المتزامنة

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

public class Program
{
  // Tiny async method: returns Task<int>
  static async Task<int> GetAnswerAsync()
  {
    // Offload simple work to a thread-pool task (demo only)
    int value = await Task.Run(() =>
    {
      Thread.Sleep(200); // simulate work
      return 42;
    });
    return value; // completes Task<int>
  }

  public static void Main(string[] args)
  {
    // In C# 6, Main cannot be async; block just for demo (console apps are safe here)
    int result = GetAnswerAsync().Result;
    Console.WriteLine("Answer = " + result);
  }
}

تركيب عمليات الانتظار

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

public class Program
{
  static async Task<int> Step1Async()
  {
    // pretend I/O
    await Task.Delay(100);
    return 10;
  }

  static async Task<int> Step2Async(int x)
  {
    await Task.Delay(100);
    return x * 3; // simple transform
  }

  static async Task<int> PipelineAsync()
  {
    int a = await Step1Async();   // await first
    int b = await Step2Async(a);  // then await second
    return a + b;                 // total 10 + 30 = 40
  }

  public static void Main(string[] args)
  {
    int total = PipelineAsync().Result; // block in demo
    Console.WriteLine("Total = " + total);
  }
}

فكرة آلة الحالات

عرض توضيحي لـ TaskCompletionSource

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

public class Program
{
  // Emulate an async source that completes later
  static Task<string> MakeTaskManually()
  {
    var tcs = new TaskCompletionSource<string>();
    // Complete on a worker after a short delay
    ThreadPool.QueueUserWorkItem(_ =>
    {
      Thread.Sleep(150);
      tcs.SetResult("done");
    });
    return tcs.Task;
  }

  static async Task<string> UseAsyncSource()
  {
    string s = await MakeTaskManually(); // await a Task you created
    return s.ToUpperInvariant();
  }

  public static void Main(string[] args)
  {
    Console.WriteLine(UseAsyncSource().Result);
  }
}

مفهوم ValueTask

آلة الحالات غير المتزامنة

مراجعة