static T?FindDescendantWithBreadthFirstSearch(DependencyObject element, ref TPredicate predicate)
{
// We're using a pooled buffer writer to amortize allocations for the temporary collection of children
// to visit for each level. The underlying array is deliberately just of type object and not DependencyObject
// to reduce the number of generic instantiations and allow the rented arrays to be reused more.
using ArrayPoolBufferWriter <object> bufferWriter = ArrayPoolBufferWriter <object> .Create();
int childrenCount = VisualTreeHelper.GetChildrenCount(element);
// Add the top level children
for (int i = 0; i < childrenCount; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(element, i);
if (child is T result && predicate.Match(result))
{
return(result);
}
bufferWriter.Add(child);
}
// Explore each depth level
for (int i = 0; i < bufferWriter.Count; i++)
{
DependencyObject parent = (DependencyObject)bufferWriter[i];
childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int j = 0; j < childrenCount; j++)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, j);
if (child is T result && predicate.Match(result))
{
return(result);
}
bufferWriter.Add(child);
}
}
return(null);
}