C#利用異步委托實現(xiàn)獲取線程返回值

更新時間：2023年12月13日 09:24:32 作者：rjcql

一般來說,異步委托主要用于解決 ThreadPool.QueueUserWorkItem 沒有提供獲取線程執(zhí)行完成后的返回值問題,下面我們就來學習一下C#如何利用異步委托實現(xiàn)獲取線程返回值吧

寫在前面

異步委托主要用于解決 ThreadPool.QueueUserWorkItem 沒有提供獲取線程執(zhí)行完成后的返回值問題。異步委托只能在.Net Framework 框架下使用，.Net Core中會報平臺錯誤，而且使用Task.Result來獲取返回值，可以達成同樣的目的；本文純粹是做個驗證試驗。

代碼實現(xiàn)

        static void Main(string[] args)
        {
            AsyncResultTest();
            Console.WriteLine("OK");
            Console.ReadKey();
        }
 
        public static void AsyncResultTest()
        {
            var str = "hello";
            var testOb = new TestOb() { msg = str };
            Func<TestOb, int> testMethod = Dosomething;
            //testMethod.BeginInvoke(testOb, Done, testMethod);
            var asyncResult = testMethod.BeginInvoke(testOb, null, null);
            var task01 = Task.Factory.StartNew(() =>
            {
                Thread.Sleep(1000);
                testOb.msg = "hello world";
                Console.WriteLine($"task01 exceuted str is {testOb.msg}");
            });
            task01.Wait();
            var result = testMethod.EndInvoke(asyncResult);
            Console.WriteLine($"AsyncResultTest finished, result is {result}");
        }
 
        private static int Dosomething(TestOb testOb)
        {
            Console.WriteLine($"Dosomething:{testOb.msg}");
            Thread.Sleep(2000);
            return testOb.msg.Length;
        }
 
        private static void Done(IAsyncResult result)
        {
            var asyncState = (Func<TestOb, int>)result.AsyncState;
            var retVal = asyncState.EndInvoke(result);
            Console.WriteLine($"result is:{retVal}");
        }
 
        class TestOb
        {
            public string msg { get; set; }
        }

執(zhí)行結果

.Net Core 下實現(xiàn)類似效果的代碼：

        public static void TaskReturnValueTest()
        {
            var value = "000";
            var task01 = Task.Factory.StartNew(() =>
            {
                value = "111";
                Thread.Sleep(1000);
                Console.WriteLine($"task01 exceuted value is {value}.");
                return "1";
            });
            var task02 = Task.Factory.StartNew(() =>
            {
                Thread.Sleep(800);
                value = "222";
                Console.WriteLine($"task02 exceuted value is {value}.");
                return "2";
            });
            Task.WaitAll(task01, task02);
            var ret01 = task01.Result;
            var ret02 = task02.Result;
            Console.WriteLine($"task01: {ret01}, task02: {ret02}");
            Console.WriteLine("Ok");
        }

執(zhí)行結果：