属性更改时引发事件

Question

当属性的值改变时，我需要引发一个事件。就我而言，这是更改 webView.Source 的时间。我无法创建派生类，因为该类被标记为已密封。有没有办法引发事件？

Answer 1

属性更改时引发事件

对于这种情况，您可以创建一个DependencyPropertyWatcher来检测DependencyProperty更改的事件。下面是可以直接使用的工具类。

public class DependencyPropertyWatcher<T> : DependencyObject, IDisposable

{

    public static readonly DependencyProperty ValueProperty =

        DependencyProperty.Register(

            "Value",

            typeof(object),

            typeof(DependencyPropertyWatcher<T>),

            new PropertyMetadata(null, OnPropertyChanged));

    public event DependencyPropertyChangedEventHandler PropertyChanged;

    public DependencyPropertyWatcher(DependencyObject target, string propertyPath)

    {

        this.Target = target;

        BindingOperations.SetBinding(

            this,

            ValueProperty,

            new Binding() { Source = target, Path = new PropertyPath(propertyPath), Mode = BindingMode.OneWay });

    }

    public DependencyObject Target { get; private set; }

    public T Value

    {

        get { return (T)this.GetValue(ValueProperty); }

    }

    public static void OnPropertyChanged(object sender, DependencyPropertyChangedEventArgs args)

    {

        DependencyPropertyWatcher<T> source = (DependencyPropertyWatcher<T>)sender;

        if (source.PropertyChanged != null)

        {

            source.PropertyChanged(source.Target, args);

        }

    }

    public void Dispose()

    {

        this.ClearValue(ValueProperty);

    }

}

用法

var watcher = new DependencyPropertyWatcher<string>(this.MyWebView, "Source");

watcher.PropertyChanged += Watcher_PropertyChanged;

private void Watcher_PropertyChanged(object sender, DependencyPropertyChangedEventArgs e)

{

}

Answer 2

您可以使用装饰器来包装原始类并为装饰属性引发事件。