/// <summary>
        ///
        /// </summary>
        public void Login()
        {
            /// <summary>
            /// when the user is logging-in he get all the names of the registreted users, and their status of connection (available, on-game, on-chat...). any update of the status of other user, or of new user that registreted will appear
            /// </summary>
            /// <param name="usersWithStatus"></param>
            ChatHubProxy.On("UpdateAllUsersNamesAndConnectionStatus", (List <UserWithStatus> usersWithStatus) =>
            {
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    usersWithStatus      = usersWithStatus.Where(x => x.UserName != UserName).ToList();
                    UsersNamesWithStatus = ConvertListToObservableCollection(usersWithStatus);
                }));
            });
            try
            {
                if (string.IsNullOrWhiteSpace(UserName) || string.IsNullOrWhiteSpace(Password))
                {
                    MessageBox.Show("You must enter a User Name and a Password, do not leave the fields empty");
                    return;
                }

                User user = new User {
                    UserName = UserName, Password = Password
                };

                Response response = ChatHubProxy.Invoke <Response>("ValidateLogin", user).Result;

                if (response.IsOk1)
                {
                    EnableButtonLogin    = false; // after login, can't do another login
                    EnableButtonRegister = false; // after login, can't do registreting
                    MessageBox.Show(response.Message1);
                }
                else if (!response.IsOk1)
                {
                    MessageBox.Show(response.Message1);
                }
            }
            catch (Exception e)
            {
                Logger.LOG.WriteToLog("Failed login in ChatViewModel" + Environment.NewLine + DateTime.Now.ToString() + Environment.NewLine + "Exception details: " + e.ToString() + "," + e.GetType().FullName + Environment.NewLine);
            }
        }
        /// <summary>
        /// when a client connect to the server, he is registering to events from the server by "ChatHubProxy.On..."
        /// </summary>
        public void ConnectToServer()
        {
            /// <summary>
            /// getting a request from other user to chat with him
            /// </summary>
            /// <param name="senderName"></param>
            ChatHubProxy.On("ChatRequest", (string senderName) =>
            {
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    bool approve = ApproveChatInvitation(senderName);
                    ChatHubProxy.Invoke("ApproveToChat", approve, UserName, senderName); // send a bolean to the server and than to the other user, if he wants to chat with him or not
                }));
            });

            /// <summary>
            /// getting a request from other user to play backgammon with him
            /// </summary>
            /// <param name="senderName"></param>
            ChatHubProxy.On("GameRequest", (string senderName) =>
            {
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    bool approve = ApproveGameInvitation(senderName);
                    ChatHubProxy.Invoke("ApproveToGame", approve, UserName, senderName); // // send a bolean to the server and than to the other user, if he wants to play bacgammon with him or not
                }));
            });

            /// <summary>
            /// get an approve or disapprove to his own chat request from the server (the server get it from the other user)
            /// </summary>
            /// <param name="approve">boolean, that approve the chat request from the other user</param>
            /// <param name="otherUser">string, the name of the other user on the chat</param>
            ChatHubProxy.On("responseOfChatRequestToSender", (bool approve, string otherUser) =>
            {
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    if (approve)
                    {
                        MessageBox.Show("Chat will start!");
                        ChatRoom chatRoom = new ChatRoom(UserName, otherUser, ChatHubProxy);
                        chatRoom.Show();
                    }
                    else
                    {
                        MessageBox.Show("Some other time...");
                    }
                }));
            });

            /// <summary>
            /// get an approve or disapprove to his own game request from the server (the server get it from the other user)
            /// </summary>
            /// <param name="approve">boolean, that approve the game request from the other user</param>
            /// <param name="otherUser">string, the name of the other user on the game</param>
            /// <param name="startGameUser">string, the user that sent the request, he will be the one that starts the game -> the "Red"</param>
            ChatHubProxy.On("responseOfGameRequestToSender", (bool approve, string otherUser, string startGameUser) =>
            {
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    if (approve)
                    {
                        string msg = "Game will start!\nPlease click the disc and then the cube in order to move a disc,\nTo get an eaten cube back to the board click only on the cube,\n";
                        if (UserName.Equals(startGameUser))
                        {
                            msg += "You are the Red,\nYou start!";
                        }
                        else if (otherUser.Equals(startGameUser))
                        {
                            msg += "You are the Black,\nThe Red starts";
                        }
                        MessageBox.Show(msg);
                        Application.Current.MainWindow.Content = new Game(UserName, otherUser, ChatHubProxy, startGameUser);
                    }
                    else
                    {
                        MessageBox.Show("Some other time...");
                    }
                }));
            });

            HubConnection.Start().Wait();
        }