What are WPF Preview Events?

by

From Programming WPF – Chris Sells and Ian Griffith

With the exception of direct events,
WPF defines most routed events in
pairs – one tunnelling and the other
bubbling. The tunnelling event name
always begins with ‘Preview’ and is
raised first. This gives parents the
chance to see the event before it
reaches the child. This is followed by
the bubbling counterpart. In most
cases, you will handle only the
bubbling one. The Preview would be
usually used to

  • block the event (e.Handled = true)
  • cause the parent to do something in advance to normal event handling.

e.g. if UI Tree = Button contains Grid contains Canvas contains Ellipse
Clicking on the ellipse would result in (MouseDownButton is eaten up by Button and Click is raised instead.)

PreviewMouseDownButton
PreviewMouseDownGrid
PreviewMouseDownCanvas
PreviewMouseDownEllipse
MouseDownEllipse
MouseDownCanvas
MouseDownGrid

More Related Contents:

  1. WPF calling commands via events
  2. What does it mean to “Capture the mouse” in WPF?
  3. Is there Selected Tab Changed Event in the standard WPF Tab Control
  4. How can I Have a WPF EventTrigger on a View trigger when the underlying Viewmodel dictates it should?
  5. How to capture a mouse click on an Item in a ListBox in WPF?
  6. How to create user define (new) event for user control in WPF ?one small example
  7. WPF Events in ResourceDictionary for a ControlTemplate
  8. WPF MouseLeftButtonUp Not Firing
  9. WPF datagrid selected row clicked event ?
  10. RoutedEventArgs.Source vs Sender
  11. How to Extract Default Control Template In Visual Studio?
  12. Keyboard shortcuts in WPF
  13. DependencyProperty getter/setter not being called
  14. Finding specific pixel colors of a BitmapImage
  15. WPF horizontal DataGrid
  16. WPF ContextMenu woes: How do I set the DataContext of the ContextMenu?
  17. WPF Datagrid set selected row
  18. What’s the difference between Dependency Property SetValue() & SetCurrentValue()
  19. inherit style from default style
  20. WPF: Setting the Width (and Height) as a Percentage Value
  21. Keyboard events in a WPF MVVM application?
  22. How to display a different value for dropdown list values/selected item in a WPF ComboBox?
  23. WPF Binding StringFormat Short Date String
  24. Custom button template in WPF
  25. Binding WPF DataGrid to DataTable using TemplateColumns
  26. WPF global font size
  27. Printing a WPF FlowDocument
  28. WPF: How to programmatically remove focus from a TextBox
  29. WPF – Bind to Item Index from within ItemTemplate of ItemsControl?
  30. WPF Databinding thread safety?

Leave a Comment