System.Action.Invoke(System.Exception)

internal void Dispose(Action<Exception> logException)
        {
            var values = Values.UnderlyingArray;

            for (int i = 0; i < values.Length; i++)
            {
                if (!(values[i] is IDisposable disposable))
                    continue;

                try
                {
                    disposable.Dispose();
                }
                catch (Exception e)
                {
                    // Eh.
                    logException(e);
                }
            }
        }

public void OnError(Exception error) => ErrorAction?.Invoke(error);

public void Launch(Action<Exception> done) {
            if (_task != null && !_task.IsCompleted) {
                throw new InvalidOperationException($"Can't launch {Id} while previous instance is {_task.Status}");
            }

            var procID = _machine.NextProcID();
            var env = new SimProc(Id, _machine, procID, _factory);
            
            _task = _factory.StartNew(async () => {
                try {
                    var engine = _launcher(env);
                    try {
                        await engine.Run();
                    } finally {
                        await engine.Dispose();
                    }
                } catch (AggregateException ex) {
                    done(ex.InnerException);
                    return;
                }
                catch (Exception ex) {
                    done(ex);
                    return;
                }

                done(null);

            }).Unwrap();
            _proc = env;

        }

public void OnError(Exception error)
        {
            _onError(error);
        }

public void StartServer(string address) {
            if (CurrentMode == Mode.Idle) {
                tmpAddress = address;
                network.StartServer(address);
            }
            else if (CurrentMode == Mode.Server) {
                var e = new Exception($"Already hosting address {Address}");
                OnServerStartFailure?.Invoke(e);
            }
            else {
                var e = new Exception($"Already connected to addr {Address}");
                OnServerStartFailure?.Invoke(e);
            }
        }

public void Connect(string address) {
            if (CurrentMode == Mode.Idle) {
                tmpAddress = address;
                network.Connect(address);
            }
            else if (CurrentMode == Mode.Client) {
                var e = new Exception("Already connected to addr " + Address);
                OnConnectionFailed?.Invoke(e);
            }
            else {
                var e = new Exception("Already connected to addr " + Address);
                OnConnectionFailed?.Invoke(e);
            }
        }

void Network_OnServerStartFailure(NetworkEvent e) {
            Reset();
            OnServerStartFailure?.Invoke(
                new Exception(e.GetDatareplacedtring() + e.Info)
            );
        }

void Network_OnConnectionFailed(NetworkEvent e) {
            Reset();
            var ex = new Exception(e.GetDatareplacedtring() + e.Info);
            OnConnectionFailed?.Invoke(ex);
        }

public static void ConnectAsync(this WebSocket socket, Action OnConnect, Action<Exception> OnError) {
			Action onDone = () => { };

			EventHandler onConnect = (sender, e) => {
				if (OnConnect != null) OnConnect();
				onDone();
			};

			EventHandler<CloseEventArgs> onClose = (sender, e) => {
				if (OnError != null) OnError(new Exception(e.Reason));
				onDone();
			};

			onDone = () => {
				socket.OnOpen -= onConnect;
				socket.OnClose -= onClose;
			};

			socket.OnOpen += onConnect;
			socket.OnClose += onClose;

			socket.ConnectAsync();
		}

void Init() {
            node.OnServerStartSuccess += () => OnCreatedChatroom?.Invoke();
            node.OnServerStartFailure += e =>
                OnChatroomCreationFailed?.Invoke(e);
            node.OnServerStop += () => OnlosedChatroom?.Invoke();

            node.OnConnectionFailed += ex => OnChatroomJoinFailed?.Invoke(ex);
            node.OnReceiveID += id => {
                if (id != 0) {
                    OnJoinedChatroom?.Invoke(id);
                    
                    OnPeerJoinedChatroom?.Invoke(0); // server joins instantly
                }
            };
            node.OnDisconnected += () => OnLeftChatroom?.Invoke();
            node.OnRemoteServerClosed += () => OnLeftChatroom?.Invoke();

            node.OnClientJoined += id => OnPeerJoinedChatroom?.Invoke(id);
            node.OnClientLeft += id => OnPeerLeftChatroom?.Invoke(id);

            node.OnPacketReceived += (sender, packet) => {
                if (packet.Tag.Equals("audio")) {
                    var reader = new BytesReader(packet.Payload);
                    var index = reader.ReadInt();
                    var frequency = reader.ReadInt();
                    var channels = reader.ReadInt();
                    var samples = reader.ReadFloatArray();

                    OnAudioReceived?.Invoke(new ChatroomAudioDTO {
                        id = sender,
                        segmentIndex = index,
                        frequency = frequency,
                        channelCount = channels,
                        samples = samples
                    });
                }
            };
        }

public void Execute(object parameter)
        {
            var nowTime = DateTime.UtcNow;
            if (_actionFrequency == TimeSpan.Zero
                || Math.Abs((nowTime - _lastActionTime).TotalMilliseconds) >= _actionFrequency.TotalMilliseconds)
            {
                _lastActionTime = nowTime;
                try
                {
                    _action.Invoke(parameter);
                }
                catch (Exception ex)
                {
                    _onExceptionAction?.Invoke(ex);
                    if (_shouldSuppressExceptions)
                    {
                        return;
                    }
                    throw ex;
                }
            }
        }

public static async Task<T> Try<T>(Func<Task<T>> taskFactory, int times, Action<Exception> onError = null)
        {
            for (var i = 1; i <= times; i++)
            {
                try
                {
                    var response = await taskFactory();
                    return response;
                }
                catch (Exception e)
                {
                    onError?.Invoke(e);
                    if (i >= times)
                    {
                        throw;
                    }
                    await Task.Delay(ExponentialBackoffTimeSlot(i) * 1000);
                }
            }
            throw new NotImplementedException("Code shall not reach here.");
        }

public void Fire<T>(Action<T> bullet, Action<Exception> handler = null)
        {
            _logger.LogInformation("Fired a new action.");
            Task.Run(() =>
            {
                using var scope = _scopeFactory.CreateScope();
                var dependency = scope.ServiceProvider.GetRequiredService<T>();
                try
                {
                    bullet(dependency);
                }
                catch (Exception e)
                {
                    _logger.LogError(e,"Cannon crashed!");
                    handler?.Invoke(e);
                }
                finally
                {
                    (dependency as IDisposable)?.Dispose();
                }
            });
        }

public void FireAsync<T>(Func<T, Task> bullet, Action<Exception> handler = null)
        {
            _logger.LogInformation("Fired a new async action.");
            Task.Run(async () =>
            {
                using var scope = _scopeFactory.CreateScope();
                var dependency = scope.ServiceProvider.GetRequiredService<T>();
                try
                {
                    await bullet(dependency);
                }
                catch (Exception e)
                {
                    _logger.LogError(e,"Cannon crashed!");
                    handler?.Invoke(e);
                }
                finally
                {
                    (dependency as IDisposable)?.Dispose();
                }
            });
        }

private async Task RunTasksInQueue()
        {
            var tasksInFlight = Task.CompletedTask;
            while (_pendingTaskFactories.Any())
            {
                while (tasksInFlight.IsCompleted && _pendingTaskFactories.Any())
                {
                    var taskFactory = _pendingTaskFactories.Dequeue();
                    tasksInFlight = taskFactory();
                }
                try
                {
                    await tasksInFlight;
                }
                catch (Exception e)
                {
                    OnError?.Invoke(e);
                }
            }
        }

[MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal static async ValueTask ForEachAction<T>(IAsyncEnumerable<T> source, Action<T> onNext, Action<Exception> onError, Action onComplete)
        {
            var enumerator = source.GetAsyncEnumerator(default);
            try
            {
                for (; ; )
                {
                    bool b;
                    try
                    {
                        b = await enumerator.MoveNextAsync();
                        if (b)
                        {
                            onNext?.Invoke(enumerator.Current);
                        }
                    }
                    catch (Exception ex)
                    {
                        onError?.Invoke(ex);
                        break;
                    }

                    if (!b)
                    {
                        onComplete?.Invoke();
                        break;
                    }

                }
            }
            finally
            {
                await enumerator.DisposeAsync();
            }
        }

public void OnError(Exception error)
        {
            DisposableHelper.WeakDispose(ref upstream);
            try
            {
                onError?.Invoke(error);
            }
            catch (Exception)
            {
                // FIXME nowhere to put these
            }
        }

void Error(Exception error, bool callTerminate)
            {
                upstream = DisposableHelper.DISPOSED;

                try
                {
                    onError?.Invoke(error);
                }
                catch (Exception ex)
                {
                    error = new AggregateException(error, ex);
                }

                if (callTerminate)
                {
                    try
                    {
                        onTerminate?.Invoke();
                    }
                    catch (Exception ex)
                    {
                        error = new AggregateException(error, ex);
                    }
                }

                downstream.OnError(error);

                try
                {
                    onAfterTerminate?.Invoke();
                }
                catch (Exception)
                {
                    // FIXME what should happen with the exception
                }

                Finally();
            }

internal void Run()
        {
            if (CurrentCount != 0)
            {
                try
                {
                    Wait();
                }
                catch (ObjectDisposedException)
                {
                    return;
                }
            }
            var ex = error;
            if (ex != ExceptionHelper.TERMINATED)
            {
                onError?.Invoke(ex);
            }
            else
            {
                onCompleted?.Invoke();
            }
        }

internal void Run()
        {
            if (CurrentCount != 0)
            {
                try
                {
                    Wait();
                }
                catch (ObjectDisposedException)
                {
                    return;
                }
            }
            var ex = error;
            if (ex != ExceptionHelper.TERMINATED)
            {
                onError?.Invoke(ex);
            }
            else
            {
                if (hasValue)
                {
                    onSuccess?.Invoke(value);
                }
                else
                {
                    onCompleted?.Invoke();
                }
            }
        }

protected override void Error(Exception ex)
        {
            onError.Invoke(ex);
        }

void OnErrorCore(Exception ex, bool callOnTerminate)
            {
                if (done)
                {
                    return;
                }
                done = true;

                try
                {
                    onError?.Invoke(ex);
                }
                catch (Exception exc)
                {
                    ex = new AggregateException(ex, exc);
                }

                if (callOnTerminate)
                {
                    try
                    {
                        onTerminate?.Invoke();
                    }
                    catch (Exception exc)
                    {
                        ex = new AggregateException(ex, exc);
                    }
                }

                downstream.OnError(ex);

                try
                {
                    onAfterTerminate?.Invoke();
                }
                catch (Exception)
                {
                    // TODO where to put these?
                }

                DoFinally();
            }

internal void Run()
        {
            if (CurrentCount != 0)
            {
                try
                {
                    Wait();
                }
                catch (ObjectDisposedException)
                {
                    return;
                }
            }
            var ex = error;
            if (ex != ExceptionHelper.TERMINATED)
            {
                onError?.Invoke(ex);
            }
            else
            {
                onSuccess?.Invoke(value);
            }
        }

public void OnError(Exception ex)
        {
            if (!DisposableHelper.IsDisposed(ref upstream))
            {
                DisposableHelper.WeakDispose(ref upstream);
                try
                {
                    onError?.Invoke(ex);
                }
                catch (Exception)
                {
                    // TODO where to put these?
                }
            }
        }

public override void OnError(Exception cause)
            {
                if (done)
                {
                    return;
                }
                done = true;
                try
                {
                    parent.onError?.Invoke(cause);
                    parent.onTerminated?.Invoke();
                }
                catch (Exception ex)
                {
                    cause = new AggregateException(cause, ex);
                }

                actual.OnError(cause);

                AfterTerminated();
            }

public void OnError(Exception cause)
            {
                if (done)
                {
                    return;
                }
                done = true;

                try
                {
                    parent.onError?.Invoke(cause);
                    parent.onTerminated?.Invoke();
                }
                catch (Exception ex)
                {
                    cause = new AggregateException(cause, ex);
                }

                actual.OnError(cause);

                OnAfterTerminate();
            }

public void Run()
        {
            for (;;)
            {
                if (SubscriptionHelper.IsCancelled(ref upstream))
                {
                    return;
                }
                if (Volatile.Read(ref wip) == 0)
                {
                    Monitor.Enter(this);
                    try
                    {
                        for (;;)
                        {
                            if (SubscriptionHelper.IsCancelled(ref upstream))
                            {
                                return;
                            }

                            if (Volatile.Read(ref wip) != 0)
                            {
                                break;
                            }
                            Monitor.Wait(this);
                        }
                    }
                    finally
                    {
                        Monitor.Exit(this);
                    }
                }
                if (queue.Poll(out T current))
                {
                    int c = consumed + 1;
                    if (c == limit)
                    {
                        consumed = 0;
                        upstream.Request(c);
                    }
                    else
                    {
                        consumed = c;
                    }
                    onNext(current);
                    Interlocked.Decrement(ref wip);
                    continue;
                }
                var ex = error;
                if (ex != null)
                {
                    onError(ex);
                }
                else
                {
                    onComplete();
                }
                return;
            }
        }

public void OnError(Exception cause)
        {
            if (SubscriptionHelper.IsCancelled(ref upstream))
            {
                return;
            }
            Volatile.Write(ref upstream, SubscriptionHelper.Cancelled);
            try
            {
                onError(cause);
            }
            catch
            {
                // TODO what should happen?
            }
        }

public void OnNext(T element)
        {
            if (SubscriptionHelper.IsCancelled(ref upstream))
            {
                return;
            }

            try
            {
                onNext(element);
            }
            catch (Exception ex)
            {
                upstream.Cancel();
                onError(ex);
            }
        }

private Action<DeliveryReport<K, V>> BuildSendCallback<TResult>(
            TaskCompletionSource<TResult> completion, 
            Action<DeliveryReport<K, V>> onSuccess,
            Action<Exception> onFailure)
        {
            return report =>
            {
                var error = report.Error;
                if (error.IsError)
                {
                    onFailure(new ProduceException<K, V>(error, report));
                }
                else
                {
                    onSuccess(report);
                    ConfirmAndCheckForCompletion();
                }
            };
        }

public void UsingTransaction(Action<SqlTransaction> onExecute, Action<Exception> onError, Action onSuccess = null!)
        {
            var transaction = Connection.BeginTransaction(IsolationLevel.ReadUncommitted);

            try
            {
                onExecute(transaction);
                transaction.Commit();
            }
            catch (Exception ex)
            {
                Log.Logger().LogError($"Transaction failed: {transaction} {Environment.NewLine} {ex.Message}");
                transaction.Rollback();
                onError(ex.GetBaseException());
            }
            finally
            {
                transaction.Dispose();
            }
        }

public void Step()
        {
            try
            {
                State.Accept(State.fetch());
                State.Eval();
            }
            catch (Exception e)
            {
                OnError?.Invoke(e);
                halt(0xFFFF, e.Message.ToLowerInvariant());
                if(State.ec)
                    WriteLine(e.ToString());
                Trace.TraceError(e.ToString());
            }
        }

public static async void Await(this Task task, Action completedCallback, Action<Exception> errorCallBack)
        {
            try
            {
                await task;
                completedCallback?.Invoke();
            }
            catch (Exception exception)
            {
                errorCallBack?.Invoke(exception);
            }
        }

public static async Task<T> AwaitTaskWithPostActionAndFinallyAndGetResult<T>(Task<T> actualReturnValue, Func<object, Task> postAction, Action<Exception> finalAction)
        {
            Exception exception = null;
            try
            {
                var result = await actualReturnValue;
                await postAction(result);
                return result;
            }
            catch (Exception ex)
            {
                exception = ex;
                throw;
            }
            finally
            {
                finalAction(exception);
            }
        }

public static async Task AwaitTaskWithPostActionAndFinally(Task actualReturnValue, Func<Task> postAction, Action<Exception> finalAction)
        {
            Exception exception = null;

            try
            {
                await actualReturnValue;
                await postAction();
            }
            catch (Exception ex)
            {
                exception = ex;
            }
            finally
            {
                finalAction(exception);
            }
        }

public static async Task<T> AwaitTaskWithPostActionAndFinallyAndGetResult<T>(Task<T> actualReturnValue, Func<Task> postAction, Action<Exception> finalAction)
        {
            Exception exception = null;

            try
            {
                var result = await actualReturnValue;
                await postAction();
                return result;
            }
            catch (Exception ex)
            {
                exception = ex;
                throw;
            }
            finally
            {
                finalAction(exception);
            }
        }

public static void FireForget(Func<Task> action, Action<Exception> handler = null)
        {
            if (action == null)
                throw new ArgumentNullException(nameof(action));

            var task = Task.Run(action);

            if (handler == null)
            {
                task.ContinueWith(
                    DefaultErrorContinuation,
                    TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.OnlyOnFaulted);
            }
            else
            {
                task.ContinueWith(
                    t => handler(t.Exception.GetBaseException()),
                    TaskContinuationOptions.ExecuteSynchronously | TaskContinuationOptions.OnlyOnFaulted);
            }
        }

public static async Task<T> TryUntil<T>(Func<Task<T>> body, Func<T?,bool> condition, int retryCount = 10, int backoffMilliSeconds = 100, int maxBackoffMilliseconds = 5000, Action<int,Exception>? onError=null, Action<Exception>? onFailed=null)
        {
            for (var i = 0; retryCount == 0 || i < retryCount; i++)
            {
                try
                {
                    var res = await body();

                    if (condition(res))
                    {
                        return res;
                    }
                }
                catch (Exception x)
                {
                    onError?.Invoke(i, x);

                    if (i == retryCount - 1)
                    {
                        onFailed?.Invoke(x);
                        throw new RetriesExhaustedException("Retried but failed", x);
                    }

                    var backoff = Math.Min(i * backoffMilliSeconds, maxBackoffMilliseconds);
                    await Task.Delay(backoff);
                }
            }

            throw new RetriesExhaustedException("Retry condition was never met");
        }

public static async Task<T> Try<T>(Func<Task<T>> body, int retryCount = 10, int backoffMilliSeconds = 100, int maxBackoffMilliseconds = 5000, Action<int,Exception>? onError=null, Action<Exception>? onFailed=null)
        {
            for (var i = 0; retryCount == 0 || i < retryCount; i++)
            {
                try
                {
                    var res = await body();
                    return res;
                }
                catch(Exception x)
                {
                    onError?.Invoke(i,x);
                    
                    if (i == retryCount - 1)
                    {
                        onFailed?.Invoke(x);
                        throw new RetriesExhaustedException("Retried but failed", x);
                    }

                    var backoff = Math.Min(i * backoffMilliSeconds, maxBackoffMilliseconds);
                    await Task.Delay(backoff);
                }
            }

            throw new RetriesExhaustedException("This should never happen...");
        }

public static async Task Try(
            Func<Task> body,
            int retryCount = 10,
            int backoffMilliSeconds = 100,
            int maxBackoffMilliseconds = 5000,
            Action<int, Exception>? onError = null,
            Action<Exception>? onFailed = null,
            bool ignoreFailure = false
        )
        {
            for (var i = 0; retryCount == 0 || i < retryCount; i++)
            {
                try
                {
                    await body();
                    return;
                }
                catch (Exception x)
                {
                    onError?.Invoke(i, x);

                    if (i == retryCount - 1)
                    {
                        onFailed?.Invoke(x);

                        if (ignoreFailure)
                            return;

                        throw new RetriesExhaustedException("Retried but failed", x);
                    }

                    var backoff = Math.Min(i * backoffMilliSeconds, maxBackoffMilliseconds);
                    await Task.Delay(backoff);
                }
            }

            throw new RetriesExhaustedException("This should never happen...");
        }

public static IDisposable Subscribe<T>(this IObservable<T> source,
            Action<T> onNext, Action<Exception> onError, Action onCompleted)
        {
            if (source == null) throw new ArgumentNullException(nameof(source));
            if (onNext == null) throw new ArgumentNullException(nameof(onNext));
            if (onError == null) throw new ArgumentNullException(nameof(onError));
            if (onCompleted == null) throw new ArgumentNullException(nameof(onCompleted));

            try
            {
                return source.Subscribe(Observer.Create(onNext, onError, onCompleted));
            }
            catch (Exception e)
            {
                onError(e);
                return Disposable.Nop;
            }
        }

public void OnError(Exception error) => _onError?.Invoke(error);

public void RegisterActorFactory<TActor>(
            ILifetimeScope container,
            Type actorServiceType,
            Func<ActorBase, IActorStateProvider, IActorStateManager> stateManagerFactory = null,
            IActorStateProvider stateProvider = null,
            ActorServiceSettings settings = null,
            object lifetimeScopeTag = null)
            where TActor : ActorBase
        {
            ActorRuntime.RegisterActorAsync<TActor>((context, actorTypeInfo) =>
            {
                ActorBase ActorFactory(ActorService actorService, ActorId actorId)
                {
                    var tag = lifetimeScopeTag ?? Constants.DefaultLifetimeScopeTag;
                    var lifetimeScope = container.BeginLifetimeScope(tag, builder =>
                    {
                        builder.RegisterInstance(context)
                            .As<StatefulServiceContext>()
                            .As<ServiceContext>();
                        builder.RegisterInstance(actorService)
                            .As<ActorService>();
                        builder.RegisterInstance(actorId)
                            .As<ActorId>();

                        ConfigurationAction(builder);
                    });

                    try
                    {
                        var actor = lifetimeScope.Resolve<TActor>();
                        return actor;
                    }
                    catch (Exception ex)
                    {
                        // Proactively dispose lifetime scope as interceptor will not be called.
                        lifetimeScope.Dispose();

                        ConstructorExceptionCallback(ex);
                        throw;
                    }
                }

                return (ActorService)container.Resolve(
                    actorServiceType,
                    new TypedParameter(typeof(StatefulServiceContext), context),
                    new TypedParameter(typeof(ActorTypeInformation), actorTypeInfo),
                    new TypedParameter(typeof(Func<ActorService, ActorId, ActorBase>), (Func<ActorService, ActorId, ActorBase>)ActorFactory),
                    new TypedParameter(typeof(Func<ActorBase, IActorStateProvider, IActorStateManager>), stateManagerFactory),
                    new TypedParameter(typeof(IStateProvider), stateProvider),
                    new TypedParameter(typeof(ActorServiceSettings), settings));
            }).GetAwaiter().GetResult();
        }

public void RegisterStatefulServiceFactory<TService>(
            ILifetimeScope container, string serviceTypeName, object lifetimeScopeTag = null)
            where TService : StatefulServiceBase
        {
            ServiceRuntime.RegisterServiceAsync(serviceTypeName, context =>
            {
                var tag = lifetimeScopeTag ?? Constants.DefaultLifetimeScopeTag;
                var lifetimeScope = container.BeginLifetimeScope(tag, builder =>
                {
                    builder.RegisterInstance(context)
                        .As<StatefulServiceContext>()
                        .As<ServiceContext>();

                    ConfigurationAction(builder);
                });

                try
                {
                    var service = lifetimeScope.Resolve<TService>();
                    return service;
                }
                catch (Exception ex)
                {
                    // Proactively dispose lifetime scope as interceptor will not be called.
                    lifetimeScope.Dispose();

                    ConstructorExceptionCallback(ex);
                    throw;
                }
            }).GetAwaiter().GetResult();
        }

public void RegisterStatelessServiceFactory<TService>(
            ILifetimeScope container, string serviceTypeName, object lifetimeScopeTag = null)
            where TService : StatelessService
        {
            ServiceRuntime.RegisterServiceAsync(serviceTypeName, context =>
            {
                var tag = lifetimeScopeTag ?? Constants.DefaultLifetimeScopeTag;
                var lifetimeScope = container.BeginLifetimeScope(tag, builder =>
                {
                    builder.RegisterInstance(context)
                        .As<StatelessServiceContext>()
                        .As<ServiceContext>();

                    ConfigurationAction(builder);
                });

                try
                {
                    var service = lifetimeScope.Resolve<TService>();
                    return service;
                }
                catch (Exception ex)
                {
                    // Proactively dispose lifetime scope as interceptor will not be called.
                    lifetimeScope.Dispose();

                    ConstructorExceptionCallback(ex);
                    throw;
                }
            }).GetAwaiter().GetResult();
        }

public IEnumerator<TDestination> GetEnumerator()
        {
            try
            {
                var results = Provider.Execute<IEnumerable<TDestination>>(Expression).Cast<object>().ToArray();
                EnumerationHandler(results);
                return results.Cast<TDestination>().GetEnumerator();
            }
            catch (Exception x)
            {
                _exceptionHandler(x);
                throw;
            }
        }

public object Execute(Expression expression)
        {
            try
            {
                Inspector.StartQueryExecuteInterceptor(null, expression);

                var sourceExpression = ConvertDestinationExpressionToSourceExpression(expression);
                var sourceResult = InvokeSourceQuery(null, sourceExpression);

                Inspector.SourceResult(sourceExpression, sourceResult);
                return sourceResult;
            }
            catch (Exception x)
            {
                _exceptionHandler(x);
                throw;
            }
        }

public TResult Execute<TResult>(Expression expression)
        {
            try
            {
                var resultType = typeof(TResult);
                Inspector.StartQueryExecuteInterceptor(resultType, expression);

                var sourceExpression = ConvertDestinationExpressionToSourceExpression(expression);

                var destResultType = typeof(TResult);
                var sourceResultType = CreateSourceResultType(destResultType);

                object destResult = null;

                // case #1: query is a projection from complex Source to complex Destination
                // example: users.UseAsDataSource().For<UserDto>().Where(x => x.Age > 20).ToList()
                if (IsProjection<TDestination>(resultType))
                {
                    // in case of a projection, we need an IQueryable
                    var sourceResult = _dataSource.Provider.CreateQuery(sourceExpression);
                    Inspector.SourceResult(sourceExpression, sourceResult);
                    
                    var queryExpressions = _mapper.ConfigurationProvider.Internal().ProjectionBuilder.GetProjection
                    (
                        sourceResult.ElementType, 
                        typeof(TDestination),
                        _parameters,
                        _membersToExpand.Select
                        (
                            m => new MemberPath
                            (
                                m.Distinct().ToArray()
                            )
                        ).ToArray()
                    );

                    destResult = (IQueryable<TDestination>)GetMapExpressions(queryExpressions).Aggregate(sourceResult, Select);
                }
                // case #2: query is arbitrary ("manual") projection
                // exaple: users.UseAsDataSource().For<UserDto>().Select(user => user.Age).ToList()
                // in case an arbitrary select-statement is enumerated, we do not need to map the expression at all
                // and cann safely return it
                else if (IsProjection(resultType, sourceExpression))
                {
                    var sourceResult = _dataSource.Provider.CreateQuery(sourceExpression);
                    var enumerator = sourceResult.GetEnumerator();
                    var elementType = ElementTypeHelper.GetElementType(typeof(TResult));
                    var constructorInfo = typeof(List<>).MakeGenericType(elementType).GetDeclaredConstructor(new Type[0]);
                    if (constructorInfo != null)
                    {
                        var listInstance = (IList)constructorInfo.Invoke(null);
                        while (enumerator.MoveNext())
                        {
                            listInstance.Add(enumerator.Current);
                        }
                        destResult = listInstance;
                    }
                }
                // case #2: projection to simple type
                // example: users.UseAsDataSource().For<UserDto>().FirstOrDefault(user => user.Age > 20)
                else
                {
                    /* 
                        in case of an element result (so instead of IQueryable<TResult>, just TResult)
                        we still want to support parameters.
                        This is e.g. the case, when the developer writes "UseAsDataSource().For<TResult>().FirstOrDefault(x => ...)
                        To still be able to support parameters, we need to create a query from it. 
                        That said, we need to replace the "element" operator "FirstOrDefault" with a "Where" operator, then apply our "Select" 
                        to map from TSource to TResult and finally re-apply the "element" operator ("FirstOrDefault" in our case) so only
                        one element is returned by our "Execute<TResult>" method. Otherwise we'd get an InvalidCastException

                        * So first we visit the sourceExpression and replace "element operators" with "where"
                        * then we create our mapping expression from TSource to TDestination (select) and apply it
                        * finally, we search for the element expression overload of our replaced "element operator" that has no expression as parameter
                            this expression is not needed anymore as it has already been applied to the "Where" operation and can be safely omitted
                        * when we're done creating our new expression, we call the underlying provider to execute it
                    */

                    // as we need to replace the innermost element of the expression,
                    // we need to traverse it first in order to find the node to replace or potential caveats
                    // e.g. .UseAsDataSource().For<Dto>().Select(e => e.Name).First()
                    //      in the above case we cannot map anymore as the "select" operator overrides our mapping.
                    var searcher = new ReplaceableMethodNodeFinder<TSource>();
                    searcher.Visit(sourceExpression);
                    // provide the replacer with our found MethodNode or <null>
                    var replacer = new MethodNodeReplacer<TSource>(searcher.MethodNode);

                    // default back to simple mapping of object instance for backwards compatibility (e.g. mapping non-nullable to nullable fields)
                    sourceExpression = replacer.Visit(sourceExpression);

                    if (replacer.FoundElementOperator)
                    {
                        /*  in case of primitive element operators (e.g. Any(), Sum()...)
                            we need to map the originating types (e.g. Enreplacedy to Dto) in this query
                            as the final value will be projected automatically
                            
                            == example 1 ==
                            UseAsDataSource().For<Dto>().Any(enreplacedy => enreplacedy.Name == "thename")
                            ..in that case sourceResultType and destResultType would both be "Boolean" which is not mappable for AutoMapper

                            == example 2 ==
                            UseAsDataSource().For<Dto>().FirstOrDefault(enreplacedy => enreplacedy.Name == "thename")
                            ..in this case the sourceResultType would be Enreplacedy and the destResultType Dto, so we can map the query directly
                        */

                        if (sourceResultType == destResultType)// && destResultType.IsPrimitive)
                        {
                            sourceResultType = typeof(TSource);
                            destResultType = typeof(TDestination);
                        }

                        var queryExpressions = _mapper.ConfigurationProvider.Internal().ProjectionBuilder.GetProjection
                        (
                            sourceResultType, 
                            destResultType, 
                            _parameters,
                            _membersToExpand.Select
                            (
                                m => new MemberPath
                                (
                                    m.Distinct().ToArray()
                                )
                            ).ToArray()
                        );
                        // add projection via "select" operator
                        var expr = GetMapExpressions(queryExpressions).Aggregate(sourceExpression, (source, lambda) => Select(source, lambda));
                        // in case an element operator without predicate expression was found (and thus not replaced)
                        var replacementMethod = replacer.ElementOperator;
                        // in case an element operator with predicate expression was replaced
                        if (replacer.ReplacedMethod != null)
                        {
                            // find replacement method that has no more predicates
                            replacementMethod = typeof(Queryable).GetAllMethods()
                                .Single(m => m.Name == replacer.ReplacedMethod.Name
#if NET45
                                            && m.GetParameters().All(p => typeof(Queryable).IsreplacedignableFrom(p.Member.ReflectedType))
#endif
                                            && m.GetParameters().Length == replacer.ReplacedMethod.GetParameters().Length - 1);
                        }

                        // reintroduce element operator that was replaced with a "where" operator to make it queryable
                        expr = Call(null,
                            replacementMethod.MakeGenericMethod(destResultType), expr);

                        destResult = _dataSource.Provider.Execute(expr);
                    }
                    // If there was no element operator that needed to be replaced by "where", just map the result
                    else
                    {
                        var sourceResult = _dataSource.Provider.Execute(sourceExpression);
                        Inspector.SourceResult(sourceExpression, sourceResult);
                        destResult = _mapper.Map(sourceResult, sourceResultType, destResultType);
                    }
                }

                Inspector.DestResult(destResult);

                // implicitly convert types in case of valuetypes which cannot be casted explicitly
                if (typeof(TResult).IsValueType() && destResult?.GetType() != typeof(TResult))
                    return (TResult)System.Convert.ChangeType(destResult, typeof(TResult));

                // if it is not a valuetype, we can safely cast it
                return (TResult)destResult;
            }
            catch (Exception x)
            {
                _exceptionHandler(x);
                throw;
            }
        }

protected override void WrapInvoke(object caller, Action action, BusinessInvokerArgs? param = null, [CallerMemberName] string? memberName = null, [CallerFilePath] string? filePath = null, [CallerLineNumber] int lineNumber = 0)
        {
            Check.NotNull(action, nameof(action));

            BusinessInvokerArgs bia = param ?? BusinessInvokerArgs.Default;
            TransactionScope? txn = null;
            OperationType ot = ExecutionContext.Current.OperationType;
            if (bia.OperationType.HasValue)
                ExecutionContext.Current.OperationType = bia.OperationType.Value;

            try
            {
                if (bia.IncludeTransactionScope)
                    txn = new TransactionScope(bia.TransactionScopeOption, TransactionScopeAsyncFlowOption.Enabled);

                action();
                txn?.Complete();
            }
            catch (Exception ex)
            {
                bia.ExceptionHandler?.Invoke(ex);
                throw;
            }
            finally
            {
                txn?.Dispose();
                ExecutionContext.Current.OperationType = ot;
            }
        }

protected async override Task WrapInvokeAsync(object caller, Func<Task> func, BusinessInvokerArgs? param = null, [CallerMemberName] string? memberName = null, [CallerFilePath] string? filePath = null, [CallerLineNumber] int lineNumber = 0)
        {
            Check.NotNull(func, nameof(func));

            BusinessInvokerArgs bia = param ?? BusinessInvokerArgs.Default;
            TransactionScope? txn = null;
            OperationType ot = ExecutionContext.Current.OperationType;
            if (bia.OperationType.HasValue)
                ExecutionContext.Current.OperationType = bia.OperationType.Value;

            try
            {
                if (bia.IncludeTransactionScope)
                    txn = new TransactionScope(bia.TransactionScopeOption, TransactionScopeAsyncFlowOption.Enabled);

                await func().ConfigureAwait(false);
                txn?.Complete();
            }
            catch (Exception ex)
            {
                bia.ExceptionHandler?.Invoke(ex);
                throw;
            }
            finally
            {
                txn?.Dispose();
                ExecutionContext.Current.OperationType = ot;
            }
        }

See More Examples