private void SendButton_OnClick(object sender, RoutedEventArgs e) { if (string.IsNullOrEmpty(MessageArea.Text) || ActualUsers.SelectedIndex < 0) { return; } var text = MessageArea.Text; var user = _usersList[ActualUsers.SelectedIndex]; _messages.Add(new Message { Date = DateTime.Now, FirstConnectionId = null, MessageText = text, SecondConnectionId = user.ConnectionId }); ActualMessages.ItemsSource = null; ActualMessages.ItemsSource = _messages; MessageArea.Text = ""; try { UpdateCipher(CipherTypeList.SelectedIndex); _hubProxy.Invoke("SendMessage", _userConnection.ConnectionId, user.ConnectionId, _cipher.Encryption(text), CipherTypeList.SelectedIndex).Wait(); } catch { MessageBox.Show("user is offline"); } }