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创建线程一种简单的方式是委托的异步调用,Delegate类提供了BeginInvoke方法,该方法可以传递委托类型定义的参数(所以BeginInvoke参数数量是可变的),另外还有2个固定的参数 回调函数委托AsynsCallBack和类型Object(如果不使用可直接赋值为null)。 BeginInvoke() 的返回值为IAsynResult,通过它的IsComplete属性可以判断异步调用是否完成。 static void Main(string[] args) { Func<int, int> act1 = new Func<int, int>(Calculate); Console.WriteLine("Main Start...."); IAsyncResult ar = act1.BeginInvoke(20,null, null); while (!ar.IsCompleted) { Console.WriteLine("Main is waiting"); Thread.Sleep(500); } int result = act1.EndInvoke(ar); Console.WriteLine("Result is " + result); Console.ReadLine(); } private static int Calculate(int total) { int sum = 0; for (int i = 0; i < total;i++ ) { sum += i; Thread.Sleep(100); } return sum; } 运行返回结果: Main Start.... 事实上,EndInvoke也是会等到异步调用结束,返回结果的。此外,IAsynResult的AsyncWaitHandle属性是WaitHandle类型,利用WaitOne()能够达到上述同样的效果,我觉得有一个好处就是可以利用WaitAll()等待多个异步调用同时完成: static void Main(string[] args) { Func<int, int> act1 = new Func<int, int>(Calculate); Func<int, int> act2 = new Func<int, int>(Calculate); Console.WriteLine("Main Start...."); IAsyncResult ar1 = act1.BeginInvoke(20,null, null); IAsyncResult ar2 = act2.BeginInvoke(30, null, null); if(WaitHandle.WaitAll(new WaitHandle[]{ar1.AsyncWaitHandle,ar2.AsyncWaitHandle},5000)) { Console.WriteLine("Waiting is over"); } int result1 = act1.EndInvoke(ar1); int result2 = act2.EndInvoke(ar2); Console.WriteLine("Result1 is {0},Result2 is {1}", result1, result2); Console.ReadLine(); } private static int Calculate(int total) { int sum = 0; for (int i = 0; i < total;i++ ) { sum += i; Thread.Sleep(100); } return sum; } 我声明了act1和act2两个委托对象,并同时进行异步调用,WaitHandle.WaitAll(new WaitHandle[]{ar1.AsyncWaitHandle,ar2.AsyncWaitHandle},5000) 等待同时完成,最后返回结果: Main Start.... 除了以上2种方式返回运行结果,还可以使用AsynsCallBack回调,BeginInvoke()的最后一个参数可以用ar.Asynstate访问,以便在回调函数中使用,例如传递委托实例获取运行结果: static void Main(string[] args) { Func<int, int> act1 = new Func<int, int>(Calculate); Console.WriteLine("Main Start...."); IAsyncResult ar1 = act1.BeginInvoke(20, new AsyncCallback(CalculateComplete), act1); while(!ar1.IsCompleted){ Console.WriteLine("Main is waiting"); Thread.Sleep(500); } Console.ReadLine(); } private static int Calculate(int total) { int sum = 0; for (int i = 0; i < total;i++ ) { sum += i; Thread.Sleep(100); } return sum; } private static void CalculateComplete(IAsyncResult ar) { Console.WriteLine("Counting is over..........."); Func<int, int> act = ar.AsyncState as Func<int, int>; Console.WriteLine("Result is "+act.EndInvoke(ar)); } 运行结果: Main Start.... 回调函数是在委托线程中完成的,还可以使用Lamda表达式,更加简便,传入最后一个参数,因为Lamda表达式可以访问域外变量: static void Main(string[] args) { Func<int, int> act1 = new Func<int, int>(Calculate); Console.WriteLine("Main Start...."); IAsyncResult ar1 = act1.BeginInvoke(20, ar => { Console.WriteLine("Result is " + act1.EndInvoke(ar)); }, null); while(!ar1.IsCompleted){ Console.WriteLine("Main is waiting"); Thread.Sleep(500); } Console.ReadLine(); }
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