private void SearchExecute()
        {
            FoundOperators = new ObservableCollection <FoundOperator>();
            var request = new OperatorCriterias();

            if (!string.IsNullOrEmpty(Username.Trim()))
            {
                request.username = Username.Trim();
            }
            else
            {
                request.username = "";
            }
            if (!string.IsNullOrEmpty(Firstname.Trim()))
            {
                request.name = Firstname.Trim();
            }
            else
            {
                request.name = "";
            }
            if (!string.IsNullOrEmpty(Lastname.Trim()))
            {
                request.surname = Lastname.Trim();
            }
            else
            {
                request.surname = "";
            }
            if (!string.IsNullOrEmpty(EMail.Trim()))
            {
                request.email = EMail.Trim();
            }
            else
            {
                request.email = "";
            }

            try
            {
                var result = WsdlRepository.SearchForOperators(request, StationRepository.GetUid(ChangeTracker.CurrentUser));
                FoundOperators = new ObservableCollection <FoundOperator>(ConvertUsers(result));
            }
            catch (System.ServiceModel.FaultException <HubServiceException> exception)
            {
                switch (exception.Detail.code)
                {
                case 178:
                    ShowError(TranslationProvider.Translate(MultistringTags.OPERATOR_NOT_FOUND).ToString());
                    return;

                default:     // 113, 114, 172
                    ShowError(exception.Detail.message);
                    return;
                }
            }
            if (FoundOperators.Count < 1)
            {
                ShowError(TranslationProvider.Translate(MultistringTags.OPERATOR_NOT_FOUND).ToString());
            }
        }