public class PersonListViewModel : INotifyPropertyChanged
    {
        #region Fields
        private string _searchText;
        private ObservableCollection<PersonModel> _resultList;
        #endregion

        #region Properties

        public ObservableCollection<PersonModel> PersonList { get
 
; private set; }

        // 查詢關鍵字
        public string SearchText
        {
            get { return _searchText; }
            set
            {
                _searchText = value;
                RaisePropertyChanged("SearchText");
            }
        }

        // 查詢結果
        public ObservableCollection<PersonModel> ResultList
        {
            
 
get { return _resultList; }
            set
            {
                _resultList = value;
                RaisePropertyChanged("ResultList");
            }
        }

        public ICommand QueryCommand
        {
            get { return new QueryCommand(Searching, CanSearching); }
        }

        
 
#endregion

        #region Construction
        public PersonListViewModel()
        {
            PersonList = PersonDataHelper.GetPersons();
            _resultList = PersonList;
        }

        #endregion

        #region Command Handler
        public void Searching()
        {
            ObservableCollection<PersonModel> personList = null;
            if (string.IsNullOrWhiteSpace(SearchText))
            {
                ResultList = PersonList;
            }
            else
            {
                personList = new ObservableCollection<PersonModel>();
                foreach (PersonModel p in PersonList)
                {
                    if (p.Name.Contains(SearchText))
                    {
                        personList.Add(p);
                    }
                }
                if (personList != null)
                {
                    ResultList = personList;
                }
            }
        }

        public bool CanSearching()
        {
            return true;
        }

        #endregion

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        #endregion

        #region Methods
        private void RaisePropertyChanged(string propertyName)
        {
            // take a copy to prevent thread issues
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        #endregion
    }