[英]Why doesn't the INotifyPropertyChanged work?
我使用Multibinding绑定了一些属性,并使用INotifyPropertyChanged接口通知这些属性的更改。但是可悲的是,似乎INotifyPropertyChanged无效。 PropertyChangedEventHandler“ PropertyChanged”始终为null。
问题:
答:能否请您告诉我为什么该事件为null?在我看来,应该为该事件设置一个默认方法PropertyChangedEventHandler,我错了吗?(已解决,谢谢!)
B.就像一些朋友说的那样,我没有使用INotifyPropertyChanged再次尝试。但是目标的属性值似乎没有改变。
性质
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); } }
多重绑定(似乎效果很好。通过使用转换器来计算受“ TopOffset”和“ LeftOffset”影响的位置)
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);
INotifyPropertyChanged
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)); }
通知变更
SetValue(LeftOffsetProperty, moveAdorner.LeftOffset); CallPropertyChanged("LeftOffset"); SetValue(TopOffsetProperty, moveAdorner.TopOffset); CallPropertyChanged("TopOffset");
您不需要为依赖项属性实现INotifyPropertyChanged。 绑定将自动跟踪这些属性的更改。
在您绑定的任何地方设置Mode=TwoWay
吗?
您需要重写OnPropertyChanged并检查该属性是否为您要查找的属性。
protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
{
if (e.Property == MyProperty)
{
// do something
}
base.OnPropertyChanged(e);
}
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