LISTBOX DRAG SCROLL

1. private void ItemsList_DragOver(object sender, System.Windows.DragEventArgs e)
2. {
3. ListBox li = sender as ListBox;
4. ScrollViewer sv = FindVisualChild<ScrollViewer>(ItemsList);
6. double tolerance = 10;
7. double verticalPos = e.GetPosition(li).Y;
8. double offset = 3;
10. if (verticalPos < tolerance) // Top of visible list?
11. {
12. sv.ScrollToVerticalOffset(sv.VerticalOffset - offset); //Scroll up.
13. }
14. else if (verticalPos > li.ActualHeight - tolerance) //Bottom of visible list?
15. {
16. sv.ScrollToVerticalOffset(sv.VerticalOffset + offset); //Scroll down.
17. }
18. }
20. public static childItem FindVisualChild<childItem>(DependencyObject obj) where childItem : DependencyObject
21. {
22. // Search immediate children first (breadth-first)
23. for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
24. {
25. DependencyObject child = VisualTreeHelper.GetChild(obj, i);
27. if (child != null && child is childItem)
28. return (childItem)child;
30. else
31. {
32. childItem childOfChild = FindVisualChild<childItem>(child);
34. if (childOfChild != null)
35. return childOfChild;
36. }
37. }
39. return null;
40. }