mono touch并行多任务处理

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//=========================创建和运行任务=========================
			Invoke (() => {
				System.Threading.Thread.Sleep (1000); 
				Tools.Alert ("after 1 second you see");
			}, 100);

			//=========================显示创建和运行任务=========================
			//不返回任务
			var task = new System.Threading.Tasks.Task (() => {
				System.Threading.Thread.Sleep (1000);
			});
			task.Start ();

			//返回任务
			var task1 = new System.Threading.Tasks.Task<int> (() => {
				System.Threading.Thread.Sleep (1000);
				return 100;
			});
			task1.Start ();
			Tools.Alert (task1.Result.ToString ());

			//=========================延续任务=========================
			System.Threading.Tasks.Task<int> TaskA = new System.Threading.Tasks.Task<int> (() => {
				return DateTime.Now.Year; 
			});
			System.Threading.Tasks.Task<String> TaskB = TaskA.ContinueWith ((a) => {
				return String.Format ("今年是{0}年", a.Result);
			});
			TaskA.Start ();
			Console.WriteLine(TaskB.Result);

			//=========================多任务延续=========================
			System.Threading.Tasks.Task<int>[] tasks = new System.Threading.Tasks.Task<int>[2];
			tasks [0] = new System.Threading.Tasks.Task<int> (() => {
				return DateTime.Now.Year; 
			});
			tasks [1] = new System.Threading.Tasks.Task<int> (() => {
				return DateTime.Now.Month;
			});
			var continuation = System.Threading.Tasks.Task.Factory.ContinueWhenAll (tasks, (antecedents) => {
				string r = string.Format ("现在是{0}年{1}月", antecedents [0].Result, antecedents [1].Result);
				Console.WriteLine (r);
			});
			tasks [0].Start ();
			tasks [1].Start ();
			continuation.Wait ();

			//=======================嵌套任务和子任务======================
			/*
				父任务是不等待子任务完成的,父任务不传播子任务引发的异常,父级状态不依赖于子状态。
			 */
			var parent = System.Threading.Tasks.Task.Factory.StartNew (() => {
				Console.WriteLine ("父任务");

				var child = System.Threading.Tasks.Task.Factory.StartNew (() => {
					System.Threading.Thread.Sleep (5000);
					Console.WriteLine ("子任务");
				});
			});

			//=======================任务取消======================
			/*
				1.简单从委托中返回。其实在多数情况下这样已经够了。但是这样取消的任务实例不
				  会转为Canceled状态而是转为RanToCompletion状态
    			2.引发 OperationCanceledException 
			 */
			var tokenSource = new System.Threading.CancellationTokenSource ();
			System.Threading.CancellationToken ct = tokenSource.Token;

			var task = System.Threading.Tasks.Task.Factory.StartNew (() => {
				ct.ThrowIfCancellationRequested ();

				bool moreToDo = true;
				while (moreToDo) {
					if (ct.IsCancellationRequested) {
						ct.ThrowIfCancellationRequested ();
					}
				}

			}, tokenSource.Token);

			tokenSource.Cancel();
			try
			{
				task.Wait();
			}
			catch (AggregateException e)
			{
				foreach (var v in e.InnerExceptions)
					Console.WriteLine(e.Message + " " + v.Message);
			}

			parent.Wait();
			Console.WriteLine("大家都完了.");