单挑这个程序很奇怪 - 编译错误？

Question

如果您通过VS2017这个小控制台程序,单步,你最终会执行两将的WriteLine(...)声明及对掷(...)声明.

这应该是绝对不可能的,那怎么可能呢？

using System;
using System.Threading.Tasks;

namespace ConsoleApp7
{
    class Program
    {
        static void Main(string[] args)
        {
           Task.Run(() => ProcAsync()).Wait();
        }


        private static async Task ProcAsync()
        {
            int aNumber = 7;

            switch (aNumber)
            {
                case 7:
                    Console.WriteLine("The value is 7");  //You first arrive here...
                    break;
                default:
                    throw new Exception("Oups..?!"); //but then also here!!!??
            }
        }

    }
}