private async Task EnqueueHistoricalMessagesAsync(CancellationToken cancellation) { await Task.Run( () => { foreach (var message in repository.GetHistoricalMessages()) { var recipient = message.To; if (!clientContollers.ContainsKey(recipient)) { var controller = new ClientController(recipient, this); clientContollers.Add(recipient, controller); } clientContollers[recipient].EnqueueMessage(message); } }, cancellation); }