這不知道是否回答你的問題......但在這裏是你將如何跟蹤總體變化可觀察集合。
要檢測對可觀察集合的更改(不會更改集合中項目的屬性),請訂閱事件ObservableCollection
。
private ObservableCollection<ViewModel> _collection;
public ObservableCollection<ViewModel> Collection {
get { return _collection; }
set {
if (_collection != value) {
// de-register on collection changed
if (_collection != null)
_collection.CollectionChanged -= this.Collection_CollectionChanged;
_collection = value;
// re-register on collection changed
if (_collection != null)
_collection.CollectionChanged += this.Collection_CollectionChanged;
}
}
private void Collection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e) {
switch (e.Action) {
case NotifyCollectionChangedAction.Add:
// e.NewItems contains the added items
break;
case NotifyCollectionChangedAction.Remove:
// e.OldItems contains the removed items
break;
case NotifyCollectionChangedAction.Replace:
// e.NewItems contains the new items,
// e.OldItems contains the removed items
break;
case NotifyCollectionChangedAction.Reset:
// the collection has been cleared
break;
}
}
如果您需要跟蹤的變化,你必須建立一個擴展ObservableCollection
訂閱了該項目的PropertyChanged
事件,然後,如果其中一個屬性已經改變引發事件的集合中的對象。
public class ObservableCollectionEx<TValue> : ObservableCollectionAddRange<TValue>
{
public ObservableCollectionEx() : base() { }
public ObservableCollectionEx(IEnumerable<TValue> values)
: base(values)
{
this.EnsureEventWiring();
}
public ObservableCollectionEx(List<TValue> list)
: base(list)
{
this.EnsureEventWiring();
}
public event EventHandler<ItemChangedEventArgs> ItemChanged;
protected override void InsertItem(int index, TValue item)
{
base.InsertItem(index, item);
var npc = item as INotifyPropertyChanged;
if (npc != null)
npc.PropertyChanged += this.HandleItemPropertyChanged;
}
protected override void RemoveItem(int index)
{
var item = this[index];
base.RemoveItem(index);
var npc = item as INotifyPropertyChanged;
if (npc != null)
npc.PropertyChanged -= this.HandleItemPropertyChanged;
}
protected override void SetItem(int index, TValue item)
{
var oldItem = this[index];
base.SetItem(index, item);
var npcOld = item as INotifyPropertyChanged;
if (npcOld != null)
npcOld.PropertyChanged -= this.HandleItemPropertyChanged;
var npcNew = item as INotifyPropertyChanged;
if (npcNew != null)
npcNew.PropertyChanged += this.HandleItemPropertyChanged;
}
protected override void ClearItems()
{
var items = this.Items.ToList();
base.ClearItems();
foreach (var npc in items.OfType<INotifyPropertyChanged>().Cast<INotifyPropertyChanged>())
npc.PropertyChanged -= this.HandleItemPropertyChanged;
}
private void HandleItemPropertyChanged(object sender, PropertyChangedEventArgs args)
{
if (typeof(TValue).IsAssignableFrom(sender.GetType()))
{
var item = (TValue)sender;
var pos = this.IndexOf(item);
this.OnItemChanged(item, pos, args.PropertyName);
}
}
protected virtual void OnItemChanged(TValue item, int index, string propertyName)
{
if (this.ItemChanged != null)
this.ItemChanged(this, new ItemChangedEventArgs(item, index, propertyName));
}
private void EnsureEventWiring()
{
foreach (var npc in this.Items.OfType<INotifyPropertyChanged>().Cast<INotifyPropertyChanged>())
{
npc.PropertyChanged -= this.HandleItemPropertyChanged;
npc.PropertyChanged += this.HandleItemPropertyChanged;
}
}
public class ItemChangedEventArgs : EventArgs
{
public ItemChangedEventArgs(TValue item, int index, string propertyName)
{
this.Item = item;
this.Index = index;
this.PropertyName = propertyName;
}
public int Index { get; private set; }
public TValue Item { get; private set; }
public string PropertyName { get; private set; }
}
}
您可以添加一些關於用戶控件的更多信息。目前還不清楚是否有事件可以讓您跟蹤由於用戶操作而添加CustomGraphic項目的時間。 – AxelEckenberger 2012-02-10 08:42:56
在ObservableCollection <>的雙向綁定中,我如何知道ViewModel中的集合已更改? – user1184598 2012-02-16 01:51:48
看到anser ......但我不確定這是你要求的。 – AxelEckenberger 2012-02-16 10:21:38