wpf更改事件前的依赖属性？

public static readonly DependencyProperty MyPropertyProperty = DependencyProperty.Register(
    "MyProperty", typeof(string), typeof(MyControl), new PropertyMetadata(default(string), OnMyPropertyChanged));

public string MyProperty
{
    get { return (string)GetValue(MyPropertyProperty); }
    set { SetValue(MyPropertyProperty, value); }
}

private static void OnMyPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    // 在这里执行更改事件前的操作
}

public static readonly DependencyProperty MyPropertyProperty = DependencyProperty.Register(
    "MyProperty", typeof(string), typeof(MyControl), new PropertyMetadata(default(string), OnMyPropertyChanged));

public string MyProperty
{
    get { return (string)GetValue(MyPropertyProperty); }
    set { SetValue(MyPropertyProperty, value); }
}

private static void OnMyPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    // 在这里执行更改事件前的操作
}

public static readonly DependencyProperty MyPropertyProperty = DependencyProperty.Register(
    "MyProperty", typeof(string), typeof(MyControl), new PropertyMetadata(default(string), null, CoerceMyProperty));

public string MyProperty
{
    get { return (string)GetValue(MyPropertyProperty); }
    set { SetValue(MyPropertyProperty, value); }
}

private static object CoerceMyProperty(DependencyObject d, object baseValue)
{
    // 在这里执行更改事件前的操作
    return baseValue;
}