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POBindingList<T> INotifyPropertyChanged unexpected behavior
 

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    <p>Suppose, I have objects:</p> <pre><code>public interface ITest { string Data { get; set; } } public class Test1 : ITest, INotifyPropertyChanged { private string _data; public string Data { get { return _data; } set { if (_data == value) return; _data = value; OnPropertyChanged("Data"); } } protected void OnPropertyChanged(string propertyName) { var h = PropertyChanged; if (null != h) h(this, new PropertyChangedEventArgs(propertyName)); } public event PropertyChangedEventHandler PropertyChanged; } </code></pre> <p>and its holder:</p> <pre><code> private BindingList&lt;ITest&gt; _listTest1; public BindingList&lt;ITest&gt; ListTest1 { get { return _listTest1 ?? (_listTest1 = new BindingList&lt;ITest&gt;() { RaiseListChangedEvents = true }); } } </code></pre> <p>Also, I subscribe to ListChangedEvent</p> <pre><code> public MainWindow() { InitializeComponent(); ListTest1.ListChanged += new ListChangedEventHandler(ListTest1_ListChanged); } void ListTest1_ListChanged(object sender, ListChangedEventArgs e) { MessageBox.Show("ListChanged1: " + e.ListChangedType); } </code></pre> <p>And 2 test handlers: For adding object</p> <pre><code> private void AddITestHandler(object sender, RoutedEventArgs e) { ListTest1.Add(new Test1 { Data = Guid.NewGuid().ToString() }); } </code></pre> <p>and for changing</p> <pre><code> private void ChangeITestHandler(object sender, RoutedEventArgs e) { if (ListTest1.Count == 0) return; ListTest1[0].Data = Guid.NewGuid().ToString(); //if (ListTest1[0] is INotifyPropertyChanged) // MessageBox.Show("really pch"); } </code></pre> <p>ItemAdded occurs, but ItemChanged not. Inside seeting proprty "Data" I found that no subscribers for my event PropertyChanged:</p> <pre><code> protected void OnPropertyChanged(string propertyName) { var h = PropertyChanged; // h is null! why?? if (null != h) h(this, new PropertyChangedEventArgs(propertyName)); } public event PropertyChangedEventHandler PropertyChanged; </code></pre> <p>Digging deeper i took reflector and discover BindingList:</p> <pre><code> protected override void InsertItem(int index, T item) { this.EndNew(this.addNewPos); base.InsertItem(index, item); if (this.raiseItemChangedEvents) { this.HookPropertyChanged(item); } this.FireListChanged(ListChangedType.ItemAdded, index); } private void HookPropertyChanged(T item) { INotifyPropertyChanged changed = item as INotifyPropertyChanged; if (changed != null) // Its seems like null reference! really?? { if (this.propertyChangedEventHandler == null) { this.propertyChangedEventHandler = new PropertyChangedEventHandler(this.Child_PropertyChanged); } changed.PropertyChanged += this.propertyChangedEventHandler; } } </code></pre> <p>Where am I wrong? Or this is known bug and i need to find some workaround? Thanks!</p>
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    1. COHow did you do the test? If you want to trigger the property changed event, you should subscribe the event first. If you have a GUI, it means you should bind the Data property to a specified control e.g. TextBox.
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      1. POBindingList<T> INotifyPropertyChanged unexpected behavior
      1. USJason Li
    2. CO@JasonLi The idea is that the BindingList should be subscribing to the event but doesn't appear to be
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      1. USAndras Zoltan
 

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