c# – 替换ObservableCollection时ListView不更新

我无法理解为什么在替换ObservableCollection(使用新的)并且未更改(添加或删除的项目)时不会刷新ListView.
我尊重属性通知的所有要求,因为我正在为我的视图模型使用DependencyObject,并且在替换集合时调用SetValue.

我有一个WPF ListView绑定到我的视图模型的Col属性：

public class ViewModel1 : DependencyObject
{
    public ViewModel1()
    {
        Col = new ObservableCollection<string>(new[] { "A","B","C","D" });
    }

    protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
    {
        base.OnPropertyChanged(e);
        Debug.WriteLine("Property changed "+ e.Property.Name);
    }   

    public ObservableCollection<string> Col
    {
        get { return (ObservableCollection<string>)GetValue(ColProperty); }
        set { SetValue(ColProperty,value); }
    }

    // Using a DependencyProperty as the backing store for MyProperty.  This enables animation,styling,binding,etc...
    public static readonly DependencyProperty ColProperty =
        DependencyProperty.Register("ColProperty",typeof(ObservableCollection<string>),typeof(ViewModel1),new PropertyMetadata(null));

}

XAML就像：

<Window x:Class="BindingPOC.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <StackPanel>
            <ListView Margin="0,10,0" ItemsSource="{Binding Col}" />
            <Button Click="Button_Click" >click</Button>
        </StackPanel>

    </Grid>
</Window>

因此,使用此代码,如果我不替换初始的ObservableCollection,一切正常.
但是当我点击按钮时.我将列表替换为：

private void Button_Click(object sender,RoutedEventArgs e)
        {
            (DataContext as ViewModel1).Col = new System.Collections.ObjectModel.ObservableCollection<string>(new[] { "Z","ZZ" });

        }

对于Col调用视图模型上的PropertyChanged方法,但ListView不更新其内容.

我是否需要保存相同的ObservableCollection引用？为什么？

public static readonly DependencyProperty ColProperty =
    DependencyProperty.Register("Col",new PropertyMetadata(null));