مشكلات عدم التزامن: التزامن فوق عدم التزامن والتعطّل المتبادل

using System;
using System.Threading.Tasks;

public class Program
{
  static async Task<string> SayHelloAsync()
  {
    await Task.Delay(200); // simulate async delay
    return "Hello";
  }

  public static void Main(string[] args)
  {
    // BAD: calling .Result blocks the thread
    string msg = SayHelloAsync().Result;
    Console.WriteLine(msg);
  }
}

using System;
using System.Threading.Tasks;

public class Program
{
  static async Task<string> SayHelloAsync()
  {
    await Task.Delay(200);
    return "Hello async";
  }

  public static void Main(string[] args)
  {
    // In C# 6, Main is sync; avoid blocking in real apps
    string msg = SayHelloAsync().GetAwaiter().GetResult(); // safer than .Result
    Console.WriteLine(msg);
  }
}

using System;
using System.Threading.Tasks;

public class Program
{
  static async Task<string> WorkAsync()
  {
    await Task.Delay(100);
    return "done";
  }

  public static void Main(string[] args)
  {
    // BAD: Wait() can also deadlock in UI/ASP.NET
    WorkAsync().Wait();
    Console.WriteLine("Completed");
  }
}