我有myType1
帶有一個依賴項屬性string Text
。我編寫了myType2
,其中包含依賴項屬性ObservableCollection<myType1> Items
。我也有Items
的圖形表示。當我按下按鈕時,它將myType1.Text
設置爲null
。當Item.Text
從Items
爲空時,我想刪除此項目。我試圖通過'綁定到列表<myType> WPF
private static void PropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
{
ObservableCollection<StringDP> ocdp = e.NewValue as ObservableCollection<StringDP>;
foreach (var sdp in ocdp)
{
if (sdp == null)
{
ocdp.Remove(sdp);
}
}
dependencyObject.SetValue(e.Property, ocdp);
}
但是當Item.Text被設置爲null時不會引發。我究竟做錯了什麼。謝謝!
更新
根據文檔ObservableCollection
當項目的屬性更改不會引發CollectionChanged
事件。我通過繼承ObservableCollection
解決了我的問題。
`public class ElObservableCollection<T>: ObservableCollection<T> where T: INotifyPropertyChanged
{
public ElObservableCollection(): base()
{
CollectionChanged += OnCollectionChanged;
}
public virtual void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.NewItems != null)
{
foreach (var item in Items)
{
item.PropertyChanged += OnItemChanged;
}
}
if (e.OldItems != null)
{
foreach (var item in Items)
{
item.PropertyChanged -= OnItemChanged;
}
}
}
private void OnItemChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == "TextProperty" && sender is StringDP)
{
StringDP sdp = sender as StringDP;
if (sdp.Text == null)
{
this.Remove((T) sender);
}
}
}
public ElObservableCollection(List<T> list)
: base(list)
{
CollectionChanged += OnCollectionChanged;
}
public ElObservableCollection(IEnumerable<T> collection)
: base(collection)
{
CollectionChanged += OnCollectionChanged;
}
}`
應該不會引發枚舉異常 - ocdp.Remove(sdp); ? – Muds 2015-03-25 08:49:52
是的,這是一個錯誤,應該是sdp.Text == null。 – metacube 2015-03-25 22:59:39