public class Program    {        static void Main(string[] args)        {             WaitForSimpleNestedTask();            Console.WriteLine("=====================================================");            SimpleNestedTask();            Thread.SpinWait(600000);//等待SimpleNestedTask结束 再运行            Console.WriteLine("=====================================================");            //SimpleNestedTaskAttachedToParent();            Console.Read();        }        static void WaitForSimpleNestedTask()        {            var outer = Task
     
      .Factory.StartNew(() =>            {                Console.WriteLine("Outer1 task executing.");                var nested = Task
      
       .Factory.StartNew(() =>                {                    Console.WriteLine("Nested1 task starting.");                    Thread.SpinWait(5000000);                    Console.WriteLine("Nested1 task completing.");                    return 42;                });                // 父任务等待子任务完成                return nested.Result;                // 父任务不等待子任务完成                //return 1;            });            //输出的时候使用了返回值outer.Result，所以自动等待父任务完成            Console.WriteLine("Outer1 has returned {0}.", outer.Result);        }        static void SimpleNestedTask()        {            var parent = Task.Factory.StartNew(() =>            {                Console.WriteLine("Outer2 task executing.");                var child = Task.Factory.StartNew(() =>                {                    Console.WriteLine("Nested2 task starting.");                    Thread.SpinWait(500000);                    Console.WriteLine("Nested2 task completing.");                });            });            //等待父任务完成，再输出字符串，如果没有这个等待，这句话会先输出            parent.Wait();            Console.WriteLine("Outer2 has completed.");         }        static void SimpleNestedTaskAttachedToParent()        {            var parent = Task.Factory.StartNew(() =>            {                Console.WriteLine("Outer3 task executing.");                var child = Task.Factory.StartNew(() =>                {                    Console.WriteLine("Nested3 task starting.");                    Thread.SpinWait(500000);                    Console.WriteLine("Nested3 task completing.");                }, TaskCreationOptions.AttachedToParent);                //增加参数TaskCreationOptions.AttachedToParent，将子任务附加进父任务，这样子任务完成后，父任务才算完成。            });                        //等待父任务完成，再输出字符串，如果没有这个等待，这句话会先输出            parent.Wait();            Console.WriteLine("Outer has completed.");        }