private async  void RemoveContactCommandExecute()
 {
     IsLoading = true;
     var messageService = ServiceLocator.Locator.Get<IMessageService>();
     var deleteCommand = new DialogCommand("remove", new RelayCommand(async () => await RemoveContactAndDeleteHistory()));
     var cancelCommand = new DialogCommand("cancel", new RelayCommand(() => { }), false, true);
     await messageService.ShowAsync("Remove", "Do you really want to remove contact and chat?", new[] { deleteCommand, cancelCommand });
     IsLoading = false;
 }
 private async void SignOutCommandExecute()
 {
     IsLoading = true;
     var messageService = ServiceLocator.Locator.Get<IMessageService>();
     DialogCommand logoutCommand = new DialogCommand("logout", new RelayCommand(SignOut));
     DialogCommand cancelCommand = new DialogCommand("cancel", new RelayCommand(() => { IsLoading = false; }), false, true);
     await messageService.ShowAsync("Logout", "Do you really want to logout?", new [] {logoutCommand, cancelCommand});
 }