//引入命名空间
using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      // Define the cancellation token.
      CancellationTokenSource source = new CancellationTokenSource();
      CancellationToken token = source.Token;

      Random rnd = new Random();
      Object lockObj = new Object();
      
      List<Task<int[]>> tasks = new List<Task<int[]>>();
      TaskFactory factory = new TaskFactory(token);
      for (int taskCtr = 0; taskCtr <= 10; taskCtr++) {
         int iteration = taskCtr + 1;
         tasks.Add(factory.StartNew( () => {
                                       int value;
                                       int[] values = new int[10];
                                       for (int ctr = 1; ctr <= 10; ctr++) {
                                          lock (lockObj) {
                                             value = rnd.Next(0,101);
                                          }
                                          if (value == 0) { 
                                             source.Cancel();
                                             Console.WriteLine("Cancelling at task {0}", iteration);
                                             break;
                                          }   
                                          values[ctr-1] = value; 
                                       }
                                       return values;
                                    }, token));   
      }
      try {
         Task<double> fTask = factory.ContinueWhenAll(tasks.ToArray(), 
                                                      (results) => {
                                                         Console.WriteLine("Calculating overall mean...");
                                                         long sum = 0;
                                                         int n = 0; 
                                                         foreach (var t in results) {
                                                            foreach (var r in t.Result) {
                                                                  sum += r;
                                                                  n++;
                                                               }
                                                         }
                                                         return sum/(double) n;
                                                      } , token);
         Console.WriteLine("The mean is {0}.", fTask.Result);
      }   
      catch (AggregateException ae) {
         foreach (Exception e in ae.InnerExceptions) {
            if (e is TaskCanceledException)
               Console.WriteLine("Unable to compute mean: {0}", 
                                 ((TaskCanceledException) e).Message);
            else
               Console.WriteLine("Exception: " + e.GetType().Name);
         }
      }
      finally {
         source.Dispose();
      }
   }
}
// Repeated execution of the example produces output like the following:
//       Cancelling at task 5
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 10
//       Unable to compute mean: A task was canceled.
//       
//       Calculating overall mean...
//       The mean is 5.29545454545455.
//       
//       Cancelling at task 4
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 5
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 6
//       Unable to compute mean: A task was canceled.
//       
//       Calculating overall mean...
//       The mean is 4.97363636363636.
//       
//       Cancelling at task 4
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 5
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 4
//       Unable to compute mean: A task was canceled.
//       
//       Calculating overall mean...
//       The mean is 4.86545454545455.