private async void OnSelectedChannel() { if (SelectedChannel != null) { SelectedChannel.HasUnreadedMessages = false; SelectedChannel.ChannelFontWeight = FontWeights.Normal; IEnumerable <Message> messages; if (SelectedChannel is PrivateGroup) { messages = await rocketChatRest.GetPrivateGroupHistory(SelectedChannel.Id); } else { messages = await rocketChatRest.GetChannelHistory(SelectedChannel.Id); } foreach (var message in messages) { message.User = Users.FirstOrDefault(x => x.Id == message.User.Id); if (message.Attachments != null && message.Attachments.Length > 0) { foreach (var attachment in message.Attachments) { attachment.ImagePreview = await rocketChatRest.GetImage(attachment.ImageUrl); } } } Messages = new ObservableCollection <Message>(messages); } }