APM 模式1

忘是亡心i 2022-05-21 09:41 127阅读 0赞

class Calculator
        {
            public IAsyncResult BeginCalculate(AsyncCallback ac, object state)
            {
                Console.WriteLine("Calling BeginCalculate on thread {0}", Thread.CurrentThread.ManagedThreadId);
                Task<string> f = Task<string>.Factory.StartNew(x => Compute(), state);
                if (ac != null)
                {
                    f.ContinueWith(x => ac(f));
                }
                return f;
            }
    
            public string Compute()
            {
                Console.WriteLine("Calling compute on thread {0}", Thread.CurrentThread.ManagedThreadId);
                Thread.Sleep(5000);
                return "3.14159265358979323846264338327950288";
            }
    
            public string EndCalculate(IAsyncResult ar)
            {
                Console.WriteLine("Calling EndCalculate on thread {0}", Thread.CurrentThread.ManagedThreadId);
                return ((Task<string>)ar).Result;
            }
        }

static void Main(string[] args)
            {
                Calculator calc = new Calculator();
    
                AsyncCallback callBack = new AsyncCallback(PrintResult);
                IAsyncResult ar = calc.BeginCalculate(callBack, calc);
    
    
                Console.WriteLine("Working...");
                Thread.Sleep(2000);
                Console.ReadLine();
            }
    
            public static void PrintResult(IAsyncResult result)
            {
                Calculator c = result.AsyncState as Calculator;
                if (c == null) return;
    
                string piString = c.EndCalculate(result);
    
                Console.WriteLine("Calling PrintResult on thread {0}; result = {1}",
                            Thread.CurrentThread.ManagedThreadId, piString);
            }

![70][]

AsyncCallback callBack = new AsyncCallback(PrintResult);

是一个实例化的异步委托回调函数，其实可以直接用

IAsyncResult ar = calc.BeginCalculate(iar => PrintResult(iar), calc);

的方式执行 。参考：[https://docs.microsoft.com/zh-cn/dotnet/standard/parallel-programming/tpl-and-traditional-async-programming][https_docs.microsoft.com_zh-cn_dotnet_standard_parallel-programming_tpl-and-traditional-async-programming]

如何：使用 Async 和 Await 并行发起多个 Web 请求 (C\#):

[https://docs.microsoft.com/zh-cn/dotnet/csharp/programming-guide/concepts/async/how-to-make-multiple-web-requests-in-parallel-by-using-async-and-await][https_docs.microsoft.com_zh-cn_dotnet_csharp_programming-guide_concepts_async_how-to-make-multiple-web-requests-in-parallel-by-using-async-and-await]

[70]: /images/20220521/bd125de629fd49bcae9e8414a7cfc5a2.png
[https_docs.microsoft.com_zh-cn_dotnet_standard_parallel-programming_tpl-and-traditional-async-programming]: https://docs.microsoft.com/zh-cn/dotnet/standard/parallel-programming/tpl-and-traditional-async-programming
[https_docs.microsoft.com_zh-cn_dotnet_csharp_programming-guide_concepts_async_how-to-make-multiple-web-requests-in-parallel-by-using-async-and-await]: https://docs.microsoft.com/zh-cn/dotnet/csharp/programming-guide/concepts/async/how-to-make-multiple-web-requests-in-parallel-by-using-async-and-await