异步方法 async/await

最新推荐文章于 2025-04-26 18:23:02 发布

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最新推荐文章于 2025-04-26 18:23:02 发布

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原文链接：http://www.cnblogs.com/ifordream/p/9913139.html

本文通过两个示例，详细对比了同步与异步操作在处理网络请求和额外操作时的效率差异。同步示例中，所有操作按顺序执行，导致整体流程阻塞；而异步示例利用Task和async/await特性，实现了并发处理，显著提升了程序的运行效率。

不用异步的示例：

static void Main(string[] args)
        {
            Watch.Start();
            string Url1 = "Http://www.tmall.com";
            string Url2 = "http://www.taobao.com";
            var result1 = CountCharacters(1, Url1);
            var result2 = CountCharacters(2, Url2);
            for (int i = 0; i < 3; i++)
            {
                ExtraOperation(i);
            }
            Console.WriteLine("{0}的字符个数{1}", Url1, result1);
            Console.WriteLine("{0}的字符个数{1}", Url2, result1);
            Console.ReadLine();
        }

        public static int CountCharacters(int id, string Url)
        {
            var wc = new WebClient();
            Console.WriteLine("开始调用：id:{0},{1}", id, Watch.ElapsedMilliseconds);
            var result = wc.DownloadString(Url);
            Console.WriteLine("调用完成：id:{0},{1}", id, Watch.ElapsedMilliseconds);
            return result.Length;
        }

        public static void ExtraOperation(int id)
        {
            var s = "";
            for (int i = 0; i < 6000; i++)
            {
                s += i;
            }
            Console.WriteLine("id={0} 的 ExtraOperation调用完成用时{1}", id, Watch.ElapsedMilliseconds);
        }

使用异步的示例

static void Main(string[] args)
        {
            Watch.Start();
            string Url1 = "Http://www.tmall.com";
            string Url2 = "http://www.taobao.com";
            Task<int> t1 = CountCharacters(1, Url1);
            Task<int> t2 = CountCharacters(2, Url2);
            for (int i = 0; i < 3; i++)
            {
                ExtraOperation(i);
            }
            Console.WriteLine("{0}的字符个数{1}", Url1, t1.Result);
            Console.WriteLine("{0}的字符个数{1}", Url2, t2.Result);
            Console.ReadLine();
        }

        public static async Task<int> CountCharacters(int id, string Url)
        {
            var wc = new WebClient();
            Console.WriteLine("开始调用：id:{0},{1}", id, Watch.ElapsedMilliseconds);
            var result = await wc.DownloadStringTaskAsync(Url);
            Console.WriteLine("调用完成：id:{0},{1}", id, Watch.ElapsedMilliseconds);
            return result.Length;
        }

        public static void ExtraOperation(int id)
        {
            var s = "";
            for (int i = 0; i < 6000; i++)
            {
                s += i;
            }
            Console.WriteLine("id={0} 的 ExtraOperation调用完成用时{1}", id, Watch.ElapsedMilliseconds);
        }