public void UserSelected(object obj) { if (SelectedUser == null) { return; } if (SelectedUsers.Count(u => u.User.UserID == SelectedUser.UserID) == 0) { if (_timeEntryFilter != null) { _timeEntryFilter.AddUser(SelectedUser); } SelectedUsers.Add(new UserFilterViewModel(SelectedUser)); OnPropertyChanged("SelectedUsers"); OnPropertyChanged("HasConsultants"); } }