1、不適用異步的示例

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Threading; using System.Net; using System.Diagnostics;namespace ConsoleApplication1 {class MyDownloadString{Stopwatch sw = new Stopwatch();private int CountCharacters(int id, string uriString){WebClient wc1 = new WebClient();Console.WriteLine("Starting call {0} : {1, 4:N0} ms", id, sw.Elapsed.TotalMilliseconds);string result = wc1.DownloadString(new Uri(uriString));Console.WriteLine(" Call {0} completed : {1, 4:N0} ms", id, sw.Elapsed.TotalMilliseconds);return result.Length;}private void CountToALargeNumber(int id, int value){for (long i = 0; i < value; i++){}Console.WriteLine(" End counting {0} : {1, 4:N0} ms", id, sw.Elapsed.TotalMilliseconds);}public void DoRun(){const int largeNumber = 6000000;const string microsoft = "http://www.microsoft.com";const string baidu = "http://www.baidu.com";sw.Start();int t1 = CountCharacters(1, microsoft);int t2 = CountCharacters(2, baidu);CountToALargeNumber(1, largeNumber);CountToALargeNumber(2, largeNumber);CountToALargeNumber(3, largeNumber);CountToALargeNumber(4, largeNumber);Console.WriteLine("Chars in {0} :{1}", microsoft, t1);Console.WriteLine("Chars in {0} :{1}", baidu, t2);}}class Program{static void Main(string[] args){MyDownloadString mds = new MyDownloadString();mds.DoRun();}}}

運行結果：

2、使用異步的示例

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Threading; using System.Net; using System.Diagnostics;namespace ConsoleApplication1 {class MyDownloadString{Stopwatch sw = new Stopwatch();private async Task<int> CountCharactersAsyc(int id, string uriString){WebClient wc1 = new WebClient();Console.WriteLine("Starting call {0} : {1, 4:N0} ms", id, sw.Elapsed.TotalMilliseconds);string result = await wc1.DownloadStringTaskAsync(new Uri(uriString));Console.WriteLine(" Call {0} completed : {1, 4:N0} ms", id, sw.Elapsed.TotalMilliseconds);return result.Length;}private void CountToALargeNumber(int id, int value){for (long i = 0; i < value; i++){}Console.WriteLine(" End counting {0} : {1, 4:N0} ms", id, sw.Elapsed.TotalMilliseconds);}public void DoRun(){const int largeNumber = 6000000;const string microsoft = "http://www.microsoft.com";const string baidu = "http://www.baidu.com";sw.Start();Task<int> t1 = CountCharactersAsyc(1, microsoft);Task<int> t2 = CountCharactersAsyc(2, baidu);CountToALargeNumber(1, largeNumber);CountToALargeNumber(2, largeNumber);CountToALargeNumber(3, largeNumber);CountToALargeNumber(4, largeNumber);Console.WriteLine("Chars in {0} :{1}", microsoft, t1.Result);Console.WriteLine("Chars in {0} :{1}", baidu, t1.Result);}}class Program{static void Main(string[] args){MyDownloadString mds = new MyDownloadString();mds.DoRun();}}}

運行結果：

3、使用返回Task<int>對象的異步方法：

using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Threading; using System.Net; using System.Diagnostics;namespace ConsoleApplication1 {static class DoAsyncStuff{private static int GetSum(int i1, int i2){Thread.Sleep(3000);return i1 + i2;}public static async Task<int> CalculateSumAsync(int i1, int i2){int sum = await Task.Run(() => GetSum(i1, i2));return sum;}}class Program{static void Main(string[] args){Stopwatch sw = new Stopwatch();ConsoleColor color = Console.ForegroundColor;sw.Start();int a1 = 5;int a2 = 6;int a3 = 2;int a4 = 3;Task<int> value = DoAsyncStuff.CalculateSumAsync(a1, a2);Task<int> value2 = DoAsyncStuff.CalculateSumAsync(a3, a4);Console.WriteLine("1)Starting... {0}ms", sw.Elapsed.TotalMilliseconds);Console.ForegroundColor = ConsoleColor.Yellow;Console.WriteLine("1)Result:[ {0}+{1}={2} ]", a1, a2, value.Result);Console.ForegroundColor = color;Console.WriteLine("1)Ended! {0}ms", sw.Elapsed.TotalMilliseconds);Console.WriteLine("2)Starting... {0}ms", sw.Elapsed.TotalMilliseconds);Console.ForegroundColor = ConsoleColor.Yellow;Console.WriteLine("2)Result:[ {0}+{1}={2} ]", a3, a4, value2.Result);Console.ForegroundColor = color;Console.WriteLine("2)Ended! {0}ms", sw.Elapsed.TotalMilliseconds);sw.Stop();}}}

運行結果：

以上程序實際上在兩個DoAsyncStuff.CalculateSumAsync異步方法中分別執行a1+a2和a3+a4的運算，調用方法即Main方法中的代碼將繼續其進程，從異步方法中獲取Task<int>的對象。當需要實際值時，就引用Task對象的Result屬性。如果異步方法設置了該屬性，調用方法就能獲得該值并繼續，否則它將暫停并等待該屬性被設置，然后再繼續執行。

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