Over on Peter McGrattan’s blog is a simple extension method for a DependencyObject which returns the visual tree descending from a particular visual element in a WPF application. The genius in Peter’s simple extension is that it automatically leverages the power of LINQ because the tree is IEnumerable:
myPanel.GetVisualOfType<TextBox>().Where(t => t.Foreground... etc
But I had a problem: the tree would not descend fully.
To cut a long story short, the issue was caused because VisualTreeHelper.GetChildrenCount doesn’t count the content of a ContentControl as a child.
The following is my version of Peter’s good work – this is just one method cut from the original class, so I implore you to head over to his blog and see the whole thing. I have made the following changes:
- Added support for ContentControl objects.
- Modified the type checking to use IsAssignableFrom so types can be collated using their base classes.
public static IEnumerable<T> GetVisualOfType<T>(this DependencyObject element)
{
return GetVisualTree(element).Where(
{
return GetVisualTree(element).Where(
t => typeof(T).IsAssignableFrom(t.GetType())).Cast<T>();
}
}
public static IEnumerable<DependencyObject> GetVisualTree(this DependencyObject element)
{
int childrenCount = VisualTreeHelper.GetChildrenCount(element);
if ((childrenCount == 0) && (element is ContentControl))
{
ContentControl cc = element as ContentControl;
if (cc.Content != null)
{
DependencyObject content = cc.Content as DependencyObject;
if (content != null)
{
yield return content;
{
int childrenCount = VisualTreeHelper.GetChildrenCount(element);
if ((childrenCount == 0) && (element is ContentControl))
{
ContentControl cc = element as ContentControl;
if (cc.Content != null)
{
DependencyObject content = cc.Content as DependencyObject;
if (content != null)
{
yield return content;
foreach (DependencyObject obj in GetVisualTree(content))
yield return obj;
}
}
}
for (int i = 0; i < childrenCount; i++)
{
var visualChild = VisualTreeHelper.GetChild(element, i);
yield return visualChild;
yield return obj;
}
}
}
for (int i = 0; i < childrenCount; i++)
{
var visualChild = VisualTreeHelper.GetChild(element, i);
yield return visualChild;
foreach (var visualChildren in GetVisualTree(visualChild))
{
yield return visualChildren;
}
}
}
Labels:
programming,
silverlight,
xaml
{
yield return visualChildren;
}
}
}
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