private void lstCust_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     if (lstCust.SelectedItem != null)
     {
         Cust cust = (Cust)lstCust.SelectedItem;
         this.Title = cust.strCustName;
     }
     else
     {
         MessageBox.Show("고객을 먼저 선택해주세요!!");
     }
 }
 private void btnSelectCust_Click(object sender, RoutedEventArgs e)
 {
     if (lstCust.SelectedItem != null)
     {
         Cust cust = (Cust)lstCust.SelectedItem;
         MessageBox.Show(cust.strCustName + "님의 전화번호는 " + cust.strCustTel + "입니다.");
     }
     else
     {
         MessageBox.Show("고객을 먼저 선택해주세요!!");
     }
 }