依赖属性'PropertyChangedCallback未被调用(Dependency Properties' PropertyChangedCallback not getting called)

 如果拥有一个带有DependencyProperty的自己的用户控件和相应的回调方法，如下所示： 
 
public partial class PieChart : UserControl
{
    public static readonly DependencyProperty RatesProperty = DependencyProperty.Register("Rates", typeof(ObservableCollection<double>), typeof(PieChart),
        new PropertyMetadata(new ObservableCollection<double>() { 1.0, 1.0 }, new PropertyChangedCallback(OnRatesChanged)));

[...]

    public static void OnRatesChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ((PieChart)d).drawChart();
    }
 
 使用此用户控件时，我将名为“Rates”的ObservableCollection绑定到RatesProperty。 费率和相关方法如下所示： 
 
private ObservableCollection<double> rates;
public ObservableCollection<double> Rates
{
    get { return this.rates; }
    set
    {
        if (this.rates != value)
        {
            this.rates = value;
            OnPropertyChanged("Rates");
        }
    }
}

public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
    if (PropertyChanged != null)
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
 
 当我更改ObservableCollection this.Rates = new ObservableCollection<double>() { 1.0, 2.0 } （例如，使用this.Rates = new ObservableCollection<double>() { 1.0, 2.0 } 1.0,2.0 this.Rates = new ObservableCollection<double>() { 1.0, 2.0 } ）时，将调用用户控件的OnRatesChanged（）方法，如预期的那样。 但是当我执行以下操作时，它不会被调用： 
 
this.Rates[0] = (double)1;
this.Rates[1] = (double)2;
OnPropertyChanged("Rates");
 
 我期望当我使用正确的属性名称引发PropertyChanged事件时，始终会调用用户控件中的相应回调。 那是错的吗？ 我找到了这个主题： 总是获取依赖属性的PropertyChangedCallback - Silverlight覆盖了Silverlight，但我认为在WPF中也是如此。 
 
 所以后台的框架检查绑定属性（在我的示例中为“Rates”）是否发生了变化，只有当它发生变化时才调用相关的回调，对吗？ 因此改变我的收藏元素没有任何效果，我总是要改变完整的收藏？ 
 
 谢谢！ 

If have an own user control with a DependencyProperty and the corresponding callback method like below:
 
public partial class PieChart : UserControl
{
    public static readonly DependencyProperty RatesProperty = DependencyProperty.Register("Rates", typeof(ObservableCollection<double>), typeof(PieChart),
        new PropertyMetadata(new ObservableCollection<double>() { 1.0, 1.0 }, new PropertyChangedCallback(OnRatesChanged)));

[...]

    public static void OnRatesChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ((PieChart)d).drawChart();
    }
 
When using this user control, I bind an ObservableCollection called "Rates" to the RatesProperty. Rates and the related methods look like this:
 
private ObservableCollection<double> rates;
public ObservableCollection<double> Rates
{
    get { return this.rates; }
    set
    {
        if (this.rates != value)
        {
            this.rates = value;
            OnPropertyChanged("Rates");
        }
    }
}

public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
    if (PropertyChanged != null)
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
 
When I change the ObservableCollection Rates (e.g. with this.Rates = new ObservableCollection<double>() { 1.0, 2.0 }) the OnRatesChanged() method of the user-control is called like expected. But when I execute the following, it is not called:
 
this.Rates[0] = (double)1;
this.Rates[1] = (double)2;
OnPropertyChanged("Rates");
 
I expected that when I raise the PropertyChanged event with the correct property name, the corresponding callback in the user control is always called. Is that wrong? I found this thread: Getting PropertyChangedCallback of a dependency property always - Silverlight which covers silverlight but I think then that the same is true in WPF.
 
So the Framework in the background checks if the bound property (in my example "Rates") changed and only if it changed, it calls the associated callback, correct? Thus changing the elements of my collection has no effect, I always have to change the complete collection?
 
Thank you!

原文：https://stackoverflow.com/questions/12745060