Reputation: 10172
I have a list box:
<ListBox x:Name="lbxAF" temsSource="{Binding}">
that gets its data from this from this modified Observable Collection:
public ObservableCollectionEx<FileItem> folder = new ObservableCollectionEx<FileItem>();
which is created within a class that uses FileSystemWatcher to monitor a specific folder for addition, deletion and modification of files.
The ObservableCollection was modified (hence the Ex at the end) so that I can modify it from an outside thread (code is not mine, I actually did some searching through this website and found it, works like a charm):
// This is an ObservableCollection extension
public class ObservableCollectionEx<T> : ObservableCollection<T>
{
// Override the vent so this class can access it
public override event System.Collections.Specialized.NotifyCollectionChangedEventHandler CollectionChanged;
protected override void OnCollectionChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
using (BlockReentrancy())
{
System.Collections.Specialized.NotifyCollectionChangedEventHandler eventHanlder = CollectionChanged;
if (eventHanlder == null)
return;
Delegate[] delegates = eventHanlder.GetInvocationList();
// Go through the invocation list
foreach (System.Collections.Specialized.NotifyCollectionChangedEventHandler handler in delegates)
{
DispatcherObject dispatcherObject = handler.Target as DispatcherObject;
// If the subscriber is a DispatcherObject and different thread do this:
if (dispatcherObject != null && dispatcherObject.CheckAccess() == false)
{
// Invoke handler in the target dispatcher's thread
dispatcherObject.Dispatcher.Invoke(DispatcherPriority.DataBind, handler, this, e);
}
// Else, execute handler as is
else
{
handler(this, e);
}
}
}
}
}
The collection is made up of these:
public class FileItem
{
public string Name { get; set; }
public string Path { get; set; }
}
which allow me to store names and paths of files.
Everything works great as far as deletion and addition of files, and the List Box gets updated flawlessly with respect to those two... however, if I change the name of any of the files, it doesn't update the list box.
How would I notify list box of the changes in FileItem's properties? I assumed that ObservableCollection would handle that, but apparently it raises flag only when FileItem is added or deleted, not when its contents are changed.
Upvotes: 3
Views: 29680
Reputation: 937
Try this simple one:
public class NotifyObservableCollection<TItem> : ObservableCollection<TItem>
where TItem : class , INotifyPropertyChanged, new()
{
#region Fields
private Action _itemPropertyChanged;
#endregion
#region Constructor
public NotifyObservableCollection(Action itemPropertyChanged)
{
_itemPropertyChanged = itemPropertyChanged;
}
#endregion
#region Methods
protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Add)
{
foreach (var item in e.NewItems)
{
var notifyItem = item as INotifyPropertyChanged;
if (notifyItem != null)
{
notifyItem.PropertyChanged += ItemPropertyChanged;
}
}
}
else if (e.Action == NotifyCollectionChangedAction.Remove)
{
foreach (var item in e.OldItems)
{
var notifyItem = item as INotifyPropertyChanged;
if (notifyItem != null)
{
notifyItem.PropertyChanged -= ItemPropertyChanged;
}
}
}
base.OnCollectionChanged(e);
}
#endregion
#region Private Methods
private void ItemPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if(_itemPropertyChanged!=null)
{
_itemPropertyChanged();
}
}
#endregion
}
Upvotes: 1
Reputation: 4109
Your FileItem
class should implement INotifyPropertyChanged
. Below is a simple working implementation of it.
public class FileItem : INotifyPropertyChanged
{
private string _Name;
public string Name
{
get { return _Name; }
set {
if (_Name != value)
{
_Name = value;
OnPropertyChanged("Name");
}
}
}
private string _Path;
public string Path
{
get { return _Path; }
set {
if (_Path != value)
{
_Path = value;
OnPropertyChanged("Path");
}
}
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(String propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Upvotes: 12
Reputation: 49620
That's how the ObservableCollection
works - it monitors only insertion/deletion/moving of items.
To update the View when each item (or FileItem
, in your case) changes, the FileItem
must implement INotifyPropertyChanged
and fire the appropriate event when you set each property that you want to observe.
Here's an example of how to do this: http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx
Upvotes: 6