使用INotifyPropertyChanged时，将再次初始化变量

Question

当我调用OnPropertyChanged（＆＃34; Something＆＃34;）时，是否可以再次声明和初始化全局变量？ 例如，我有这段代码：

private ObservableCollection<MatchesViewModel> matches;
private ObservableCollection<string> listWithLists;
private string directoryName = "currentMatches";

private void HandleLoadListClicked(object obj)
{
    directoryName = selectedItem;
    this.Matches = DataGetterAndSetter.GetMatches("Lists\\" + directoryName + ".xml");
    MainPage window = new MainPage();
    window.Show();
}

public IEnumerable<MatchesViewModel> Matches
{
    get
    {
        matches = DataGetterAndSetter.GetMatches("Lists\\"+ directoryName + ".xml");
        return this.matches;
    }
    set
    {
        if (matches == null)
        {
            matches = new ObservableCollection<MatchesViewModel>();
        }
        matches.Clear();
        foreach (var item in value)
        {
            matches.Add(item);
        }
        this.OnPropertyChanged("Matches");
    }
}

public event PropertyChangedEventHandler PropertyChanged;

protected void OnPropertyChanged(string propertyName)
{
    if (this.PropertyChanged != null)
    {
        var propertyChangedEventArgs = new PropertyChangedEventArgs(propertyName);
        this.PropertyChanged(this, propertyChangedEventArgs);
    }
}

每当OnPropertyChanged（＆＃34; Matches＆＃34;）被省略时，将在类的开头使用它的默认值 - ＆＃34; currentMatches＆＃34;再次初始化directoryName变量。这是正常的，我如何保存directoryName的值，以便以后在我获取属性中的数据时使用它？