WPF - 如何从按钮处理程序确定列表框中当前项的索引

<ListBox x:Name="myListBox" SelectionChanged="myListBox_SelectionChanged">
    <ListBoxItem>Item 1</ListBoxItem>
    <ListBoxItem>Item 2</ListBoxItem>
    <ListBoxItem>Item 3</ListBoxItem>
</ListBox><Button x:Name="myButton" Content="Get Current Index" Click="myButton_Click" />

private void myListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    // 在此处理列表框的选择更改事件
}

private void myButton_Click(object sender, RoutedEventArgs e)
{
    int currentIndex = myListBox.SelectedIndex;
    MessageBox.Show("当前项的索引是：" + currentIndex);
}