Question

I have the following controls:

<UserControl >

   <!--<ScrollViewer >-->
       <Viewbox >
           <Canvas/>
       </Viewbox>
   <!--</ScrollViewer>-->

</UserControl>

I want to add and remove dynamically the ScrollViewer as my ViewBox parent (for example when I click a Button):

private void Button_Click(object sender, RoutedEventArgs e)
{
    // Here add or remove ScrollViewer
}

How can I do?

Answer 1

Assuming your UserControl is named userControl:

private void Button_Click(object sender, RoutedEventArgs e)
{
    var scrollViewer = userControl.Content as ScrollViewer;
    if (scrollViewer != null)
    {
        var content = scrollViewer.Content;
        scrollViewer.Content = null;
        userControl.Content = content;
    }
    else
    {
        var content = userControl.Content;
        userControl.Content = null;
        userControl.Content = new ScrollViewer { Content = content };
    }
}

Why set the Content to null, you might wonder? Because WPF won’t let you have one element be the child of two elements at once, and immediately throws an exception if you try to do that (e.g. by just saying userControl.Content = scrollViewer.Content;).