why IAsyncResult returning this error? System.PlatformNotSupportedException: 'Operation is not supported on this platform.'

Question

I'm trying to write a delegate with IAsyncResult type in unit test. I expect to see 2 different thread ids in output debug but I encounter this error:

System.PlatformNotSupportedException: 'Operation is not supported on this platform.'

Here is my code:

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Diagnostics;

namespace UnitTest
{

    [TestClass]
    public class UnitTest1
    {
       // public delegate void stuff();
        public void dowork()
        {
            Debug.WriteLine("Hello world");
            Debug.WriteLine
                (System.Threading.Thread.CurrentThread.ManagedThreadId.ToString());
        }
        [TestMethod]
        public void demo01()
        {
            Debug.WriteLine
                (System.Threading.Thread.CurrentThread.ManagedThreadId.ToString());
            Action s = dowork;
           IAsyncResult result= s.BeginInvoke(null,null);
            s.EndInvoke(result);
          //  stuff s = new stuff(dowork);
            s();
        }
    }
}

at this line I got that error:

IAsyncResult result= s.BeginInvoke(null,null);

I am using VS 2017. After researching I got that it works on unit test (framework), but it's not supported in unit test(.netcor). Anyone know why and any solution for that?