silverlight textbox scrollbarvisibility

I have a text box with verticalscrollbarvisibility set 开发者_JS百科to auto. I would like to do a test to find out if the scrollbar is actually visible during runtime. I have tried the statement:

if (textbox1.VerticalScrollBarVisibility == ScrollBarVisibility.Visible)

but it does not work. Any ideas?

---

First place the following extension method in static class (either place the class in the same namespace as the rest of your code or in namespace included with a using statement in your code file):-

public static IEnumerable<DependencyObject> Descendents(this DependencyObject root)
{
    int count = VisualTreeHelper.GetChildrenCount(root);
    for (int i = 0; i < count; i++)
    {
        var child = VisualTreeHelper.GetChild(root, i);
        yield return child;
        foreach (var descendent in Descendents(child))
            yield return descendent;
    }
}

With this extension method available you can dig out the ScrollViewer inside the text box which is responsible for the scroll bar and test its ComputedVerticalScrollBarVisibility.

if (textbox1.Descendents().OfType<ScrollViewer>()
  .FirstOfDefault().ComputedVerticalScrollBarVisibility == Visibility.Visible)