using System;
using System.Linq;
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.Reflection;
using System.Linq.Expressions;
using System.Threading;
using System.Threading.Tasks;

var local = new AsyncLocal<string?>();
local.Value = "parent";
var gate = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
Task child = Child();
Console.WriteLine($"parent-before:{local.Value}");
gate.SetResult(true);
await child;
Console.WriteLine($"parent-after:{local.Value}");
async Task Child() { local.Value = "child"; await gate.Task; Console.WriteLine($"child:{local.Value}"); }