创建任务

Task.Factory.StartNew
线程池

等待任务

Task.WaitAll(taskArray);

using System;
using System.Threading;
using System.Threading.Tasks;

class CustomData
{
   public long CreationTime;
   public int Name;
   public int ThreadNum;
}

public class Example
{
   public static void Main()
   {
      Task[] taskArray = new Task[10];
      for (int i = 0; i < taskArray.Length; i++) {
         taskArray[i] = Task.Factory.StartNew( (Object obj ) => {
                                                  CustomData data = obj as CustomData;
                                                  if (data == null)
                                                     return;

                                                  data.ThreadNum = Thread.CurrentThread.ManagedThreadId;
                                               },
                                               new CustomData() {Name = i, CreationTime = DateTime.Now.Ticks} );
      }
      Task.WaitAll(taskArray);
      foreach (var task in taskArray) {
         var data = task.AsyncState as CustomData;
         if (data != null)
            Console.WriteLine("Task #{0} created at {1}, ran on thread #{2}.",
                              data.Name, data.CreationTime, data.ThreadNum);
      }
   }
}
// The example displays output like the following:
//       Task #0 created at 635116412924597583 on thread #3.
//       Task #1 created at 635116412924607584 on thread #4.
//       Task #3 created at 635116412924607584 on thread #4.
//       Task #4 created at 635116412924607584 on thread #4.
//       Task #2 created at 635116412924607584 on thread #3.
//       Task #6 created at 635116412924607584 on thread #3.
//       Task #5 created at 635116412924607584 on thread #4.
//       Task #8 created at 635116412924607584 on thread #4.
//       Task #7 created at 635116412924607584 on thread #3.
//       Task #9 created at 635116412924607584 on thread #4.

嵌套子任务

线程套线程，创建线城市添加TaskCreationOptions.AttachedToParent配置，这样子任务完成父任务才会完成
官方推荐分离子任务即个玩个的

using System;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      var parent = Task.Factory.StartNew(() => {
            Console.WriteLine("Parent task executing.");
            var child = Task.Factory.StartNew(() => {
                  Console.WriteLine("Attached child starting.");
                  Thread.SpinWait(5000000);
                  Console.WriteLine("Attached child completing.");
            }, TaskCreationOptions.AttachedToParent);
      });
      parent.Wait();
      Console.WriteLine("Parent has completed.");
   }
}
// The example displays the following output:
//       Parent task executing.
//       Attached child starting.
//       Attached child completing.
//       Parent has completed.

参考

• https://docs.microsoft.com/zh-cn/dotnet/standard/parallel-programming/task-based-asynchronous-programming
• https://docs.microsoft.com/zh-cn/dotnet/standard/parallel-programming/attached-and-detached-child-tasks