async,await與task.wait()或task.Result的區別

你是否曾經與我一樣不理解async,await與task.wait()或者task.Result的區別？

接下來，一個Demo讓你看出他們之間的區別。

  static void Main(string[] args)
        {
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:start");

            Test(); //不等待
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:end");
            Console.Read();
        }

        static Task<int> Sleep()
        {
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Sleep start");
            Thread.Sleep(1000);
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Sleep end");
            return Task.FromResult(100);
        }
        
        static Task<int> Test()
        {
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Test start");
            var a=Task.Run(Sleep).Result;//由上一篇文章可知Run將會在線程池內調度執行
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Test end");
            return Task.FromResult(a);
        }

 

運行結果：

1:start
1:Test start
4:Sleep start
4:Sleep end
1:Test end
1:end

由此可以看出Task.Result會阻塞主線程。

 

 static void Main(string[] args)
        {
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:start");

            TestAsync();//不等待

            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:end");
            Console.Read();
        }

        static Task<int> Sleep()
        {
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Sleep start");
            Thread.Sleep(1000);
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Sleep end");
            return Task.FromResult(100);
        }
        
        static async Task<int> TestAsync()
        {
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Test start");
            var a = await Task.Run(Sleep);
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Test end");
            return a;
        }

運行結果：

1:start
1:Test start
4:Sleep start
1:end
4:Sleep end
4:Test end

async,await不會阻塞主線程