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POWhy doesn't the INotifyPropertyChanged work?
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copied!<p>I used a Multibinding to bind some properties and use the INotifyPropertyChanged interface to notify these properties'changes.But sadly,it seems that the INotifyPropertyChanged didn't work. The PropertyChangedEventHandler "PropertyChanged" was null all the time.</p> <p>Questions:</p> <p>A. Could you please tell me why the event is null?In my mind,there should be a default method for the event PropertyChangedEventHandler,am I wrong?(Resolved,thanks!)</p> <p>B. Just like some friends said,I tried again without using the INotifyPropertyChanged.But the target's property's value seems to be not changed...</p> <hr> <ol> <li><p>Properties</p> <pre><code>public static readonly DependencyProperty LeftOffsetProperty = DependencyProperty.Register("LeftOffset", typeof(double), typeof(NetworkTaskLable), new FrameworkPropertyMetadata(0d, FrameworkPropertyMetadataOptions.AffectsRender)); public static readonly DependencyProperty TopOffsetProperty = DependencyProperty.Register("TopOffset", typeof(double), typeof(NetworkTaskLable), new FrameworkPropertyMetadata(0d, FrameworkPropertyMetadataOptions.AffectsRender)); public double LeftOffset { get { return (double)GetValue(LeftOffsetProperty); } set { SetValue(LeftOffsetProperty, value); } } public double TopOffset { get { return (double)GetValue(TopOffsetProperty); } set { SetValue(TopOffsetProperty, value); } } </code></pre></li> <li><p>Multibinding (It seems work well.By using the converter to calculate a location which is affected by "TopOffset" and "LeftOffset")</p> <pre><code>var multibinding = new MultiBinding() { Converter = new BeginAndStartDateToLeftConverter_NetworkTaskLable(), ConverterParameter = NetworkView }; multibinding.Bindings.Add(new Binding("Start")); multibinding.Bindings.Add(new Binding("StartDate") { Source = NetworkView }); multibinding.Bindings.Add(new Binding("LeftOffset") { Source = this }); MainCanvas.SetBinding(LeftProperty, multibinding); </code></pre></li> <li><p>INotifyPropertyChanged</p> <pre><code>public event PropertyChangedEventHandler PropertyChanged; public void CallPropertyChanged(string PropertyName) { if (PropertyChanged != null)//It seems to be null all the time!!!And the properties'changes were never notified!!! PropertyChanged(this, new PropertyChangedEventArgs(PropertyName)); } </code></pre></li> <li><p>Notify the change </p> <pre><code>SetValue(LeftOffsetProperty, moveAdorner.LeftOffset); CallPropertyChanged("LeftOffset"); SetValue(TopOffsetProperty, moveAdorner.TopOffset); CallPropertyChanged("TopOffset"); </code></pre></li> </ol>

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