private void RemoveHost(object selected)
 {
     if (SelectedItem != null)
     {
         HostCollectionView.Remove(SelectedItem);
     }
     else
     {
         MessageBox.Show("선택한 항목이 없습니다.");
     }
 }
 private void RegisterHost(object parameter)
 {
     if (!(HostCollectionView.Where(x => x.hostname == InputHostname).Count() > 0))
     {
         HostCollectionView.Add(new TargetHost {
             hostname = InputHostname, block = InputAllowRadio ? false: true, comment = InputComment
         });
         OnPropertyChanged();
     }
     else
     {
         MessageBox.Show(string.Format("{0} : 이미 등록된 호스트 입니다.", InputHostname));
     }
 }