public ContactListViewModel(ContactListProvider contactListProvider) { this.contactListProvider = contactListProvider; CollectionViewSource.GetDefaultView(ContactList).Filter = o => { var contactDetail = (ContactDetailViewModel)o; return(SearchedText.IsNullOrEmpty() || contactDetail.FirstName.Contains(SearchedText, StringComparison.OrdinalIgnoreCase) || contactDetail.LastName.Contains(SearchedText, StringComparison.OrdinalIgnoreCase)); }; // UpdateContactList(); }