ClrmdAsyncLocal.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using Microsoft.Diagnostics.Runtime;

namespace ClrmdAsyncLocal
{
    internal class Program
    {
        static void Main(string[] args)
        {
            const string path = @"C:\Users\kevin.gosse\Desktop\blog\asynclocal\ClientApp.exe_210916_114422.dmp";

            var target = DataTarget.LoadDump(path);
            var runtime = target.ClrVersions.First().CreateRuntime();
            var heap = runtime.Heap;

            var array = heap.GetProxies<AsyncLocal<int>[]>().First();

            foreach (var item in array)
            {
                Console.WriteLine($"Values stored in AsyncLocal {item}:");

                foreach (var (threadId, value) in ExtractAsyncLocalValues(heap, (ulong)item))
                {
                    Console.WriteLine($" - {threadId}: {(int)value}");
                }
            }

            Console.ReadLine();
        }

        private static IEnumerable<(int threadId, dynamic value)> ExtractAsyncLocalValues(ClrHeap heap, ulong address)
        {
            foreach (var thread in heap.GetProxies<Thread>())
            {
                int threadId = thread._managedThreadId;
                var localValues = thread._executionContext?.m_localValues;

                foreach ((dynamic key, dynamic value) pair in ReadAsyncLocalStorage(localValues))
                {
                    if ((ulong)pair.key == address)
                    {
                        yield return (threadId, pair.value);
                        break;
                    }
                }
            }
        }

        private static IEnumerable<(dynamic key, dynamic value)> ReadAsyncLocalStorage(dynamic storage)
        {
            if (storage == null)
            {
                return Enumerable.Empty<(dynamic key, dynamic value)>();
            }

            ClrType type = storage.GetClrType();

            return type.Name switch
            {
                "System.Threading.AsyncLocalValueMap+OneElementAsyncLocalValueMap" => ReadOneElementAsyncLocalValueMap(storage),
                "System.Threading.AsyncLocalValueMap+TwoElementAsyncLocalValueMap" => ReadTwoElementAsyncLocalValueMap(storage),
                "System.Threading.AsyncLocalValueMap+ThreeElementAsyncLocalValueMap" => ReadThreeElementAsyncLocalValueMap(storage),
                "System.Threading.AsyncLocalValueMap+MultiElementAsyncLocalValueMap" => ReadMultiElementAsyncLocalValueMap(storage),
                "System.Threading.AsyncLocalValueMap+ManyElementAsyncLocalValueMap" => ReadManyElementAsyncLocalValueMap(storage),
                _ => throw new InvalidOperationException($"Unexpected asynclocal storage type: {type.Name}")
            };
        }

        private static IEnumerable<(dynamic key, dynamic value)> ReadOneElementAsyncLocalValueMap(dynamic storage)
        {
            yield return (storage._key1, storage._value1);
        }

        private static IEnumerable<(dynamic key, dynamic value)> ReadTwoElementAsyncLocalValueMap(dynamic storage)
        {
            yield return (storage._key1, storage._value1);
            yield return (storage._key2, storage._value2);
        }

        private static IEnumerable<(dynamic key, dynamic value)> ReadThreeElementAsyncLocalValueMap(dynamic storage)
        {
            yield return (storage._key1, storage._value1);
            yield return (storage._key2, storage._value2);
            yield return (storage._key3, storage._value3);
        }

        private static IEnumerable<(dynamic key, dynamic value)> ReadMultiElementAsyncLocalValueMap(dynamic storage)
        {
            foreach (var kvp in storage._keyValues)
            {
                yield return (kvp.key, kvp.value);
            }
        }

        private static IEnumerable<(dynamic key, dynamic value)> ReadManyElementAsyncLocalValueMap(dynamic storage)
        {
            foreach (var entry in storage._entries)
            {
                if (entry.key != null)
                {
                    yield return (entry.key, entry.value);
                }
            }
        }
    }
}