C#中Await/Async中的线程ID疑惑

今天写了个测试的代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;

namespace ConsoleApp2
{
   public class AwaitAsyncClassNew
    {
        public async Task<int> Show() {
            Console.WriteLine($"aaaaaa.....{ Thread.CurrentThread.ManagedThreadId }");
            await Task.Run(
                    () => {
                        Console.WriteLine($"bbbbbbbbbbb.....{ Thread.CurrentThread.ManagedThreadId }");
                        Thread.Sleep(5000);
                        Console.WriteLine($"cccccccccccccc.....{ Thread.CurrentThread.ManagedThreadId }");
                    }
                );
            Console.WriteLine($"dddddddddddddd.....{ Thread.CurrentThread.ManagedThreadId }");

            return 1;
        }
    }
}

运行结果如下:

 用反编译工具查看,代码经过编译后，变成如下的了：

编译后，代码用 TaskAwaiter来实现了，我又写了一个例子,代码如下:

 public void TestTaskAwait() {
            Console.WriteLine($"This is Main Start.... {  Thread.CurrentThread.ManagedThreadId }");

            TaskAwaiter awaiter = Task.Run(() => {
                Console.WriteLine($"This is Task Start.... {  Thread.CurrentThread.ManagedThreadId }");

                Thread.Sleep(2000);

                Console.WriteLine($"This is Task End.... {  Thread.CurrentThread.ManagedThreadId }");
            }).GetAwaiter();
            while (!awaiter.IsCompleted) {
                Thread.Sleep(100);
            }
            awaiter.GetResult();
            Console.WriteLine($"This is Main End.... {  Thread.CurrentThread.ManagedThreadId }");
        }

运行结果如下:

 此时猜测,是代码:

 <>t__builder.AwaitUnsafeOnCompleted(ref awaiter, ref this); 这行代码在作怪。(把当前运行的线程池改成子线程运行的线程池了)这个只是猜测

            awaiter.GetResult();
            Console.WriteLine($"dddddddddddddd.....{Thread.CurrentThread.ManagedThreadId}");
            result = 1;

把这些代码都丢在新开启的子线程中在运行了。暂时还没找到依据。我的慢慢看，有谁知道的，请帮我解惑下。