using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
using System.Web.Mvc;

namespace WebApplication1.Controllers
{
    public class HomeController : Controller
    {
        public async Task<ActionResult> Index()
        {
            await MyMethod();

            return View();
        }

        public async Task MyMethod()
        {
            Debug.WriteLine(SynchronizationContext.Current); // AspNetSyncronizationContext

            SynchronizationContext.SetSynchronizationContext(new CustomSyncContext());
            Debug.WriteLine(SynchronizationContext.Current); // WebApplication1.Controllers.HomeController.CustomSyncContext

            await SomeAsyncMethod().ConfigureAwait(true);
            Debug.WriteLine(SynchronizationContext.Current); //null
        }

        public async Task SomeAsyncMethod()
        {
            await Task.Delay(TimeSpan.FromSeconds(5));
        }

        public class CustomSyncContext : SynchronizationContext { }

    }
}