Detect, if ScrollBar of ScrollViewer is visible or not

Question

I have a TreeView. Now, I want to detect, if the vertical Scrollbar is visible or not. When I try it with

var visibility = this.ProjectTree.GetValue(ScrollViewer.VerticalScrollBarVisibilityProperty)

(where this.ProjectTree is the TreeView) I get always Auto for visibility.

How can I do this to detect, if the ScrollBar is effectiv visible or not?

Thanks.

Answer 1

You can use the ComputedVerticalScrollBarVisibility property. But for that, you first need to find the ScrollViewer in the TreeView's template. To do that, you can use the following extension method:

    public static IEnumerable<DependencyObject> GetDescendants(this DependencyObject obj)
    {
        foreach (var child in obj.GetChildren())
        {
            yield return child;
            foreach (var descendant in child.GetDescendants())
            {
                yield return descendant;
            }
        }
    }

Use it like this:

var scrollViewer = ProjectTree.GetDescendants().OfType<ScrollViewer>().First();
var visibility = scrollViewer.ComputedVerticalScrollBarVisibility;