private void checkFilter() { if (comboBoxSearch.SelectedItem != null && comboBoxSearch.SelectedItem.ToString() != "" && textBoxSearch.Text.ToString() != "") { var listBillss = db.Bills.ToList(); var filterBills = listBillss.FindAll(Bills => Bills.GetType().GetProperty(comboBoxSearch.SelectedItem.ToString()).GetValue(Bills).ToString() == textBoxSearch.Text.ToString()); dataGridView.DataSource = filterBills; } else { dataGridView.DataSource = getDataSource(); } }