async,await与task.wait()或task.Result的区别

你是否曾经与我一样不理解async,await与task.wait()或者task.Result的区别？

接下来，一个Demo让你看出他们之间的区别。

  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($"{Thread.CurrentThread.ManagedThreadId}:Test start");
            var a=Task.Run(Sleep).Result;//由上一篇文章可知Run将会在线程池内调度执行
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}:Test end");
            return Task.FromResult(a);
        }

运行结果：

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

由此可以看出Task.Result会阻塞主线程。

 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;
        }

运行结果：

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

async,await不会阻塞主线程