private void btnFind_Click(object sender, RoutedEventArgs e) { string id = null; string tdateStr = null; string patient = null; string dentist = null; if (idChk.IsChecked.Value) { id = keywordTxt.Text.ToLower(); } if (tDateChk.IsChecked.Value) { tdateStr = keywordTxt.Text.ToLower(); } if (patientChk.IsChecked.Value) { patient = keywordTxt.Text.ToLower(); } if (dentistChk.IsChecked.Value) { dentist = keywordTxt.Text.ToLower(); } DateTime tdate = DateTime.Now; bool err = false; try { tdate = DateTime.Parse(tdateStr); } catch (Exception ex) { err = true; } Treatments = DB.findTreatmentsByOr(id, (err ? null :tdateStr), patient, dentist); DataContext = Treatments; }