[W8App] ListBox Binding data (5) – notify count changed

要如何得知ListBox繫結的資料數量有變化呢？由於資料來源是透過繫結，所以要得知資料量有有更動時必需加入聆聽ListBox.Items.VectorChanged事件。

   1: myListBox.Items.VectorChanged += VectorChangedEventHandler;

當數量改變時，會呼叫指定的VectorChangedEventHander函式：

   1: public void VectorChangedEventHandler(IObservableVector<object> sender, IVectorChangedEventArgs e)

   2: {

   3:     myListBox.Visibility = (sender.Count > 0) ? Visibility.Visible : Visibility.Collapsed;

   4:  

   5:     String strValue = String.Format(@"({0})", sender.Count);

   6:  

   7:     Debug.WriteLine(strValue);

   8: }