1. Important New Concepts In WPF
Orlando Robertson
Brown Bag Seminar
Windows Presentation Foundation Unleashed

2. Introduction This chapter introduces concepts beyond .NET programming
New Concepts
Logical Trees
Visual Trees
Extended Concepts
Dependency Properties
Routed Events
Commands
Review UI applications needed for programming

3. Logical & Visual Trees Logical Trees are objects to create UIs in WPF
Important because every aspect in WPF is associated to Logical Trees
Visual Trees are considered an expanded logical tree exposing visual components
Visual Trees expose elements derived from System.Windows.Media.Visual &Visual3D

4. Logical & Visual Trees

5. Logical & Visual Trees

6. Logical & Visual Trees
Visual Trees & Logical Trees are needed for applications separating look and logic
Logical Trees can be traversed using class System.Windows.LogicalTreeHelper
Visual Trees can be traversed using class System.Windows.VisualTreeHelper

7. Dependency Properties
Dependency Property is a new WPF property type used to enable styling, automatic data binding, animation
Dependency Properties provide change notifications from declarative markup
Also property value inheritance & multiple provider support
Styling and Animation are done with dependency properties

8. A Dependency Property Implementation
Dependency Properties are .NET properties connected to extra WPF infrastructure
Represented by System.Windows.DependencyProperty
Created by calling DependencyProperty.Register
Options for passing metadata, callbacks, coercing values, validating values
.NET property wrappers are bypassed at run-time when setting Dependency Properties in XAML

9. Change Notification
Change Notifications allows WPF to automatically trigger actions when dependency properties change
Property Trigger, Data Trigger, Event Trigger
Property Trigger allows custom changes when property values change without procedural code
Data Trigger works for all .NET properties, not just dependency properties
Event Trigger declaratively specifies actions for raised events
Used for animation and sound applications

10. Property Value Inheritance
Property Value Inheritance refers to flow of property values down the element tree
Child elements inherit properties of the parent element unless overridden
Elements deriving from Freezable may inherit values from the parent element

11. Support for Multiple Providers
WPF executes a 5 step process to calculate the final value of dependency properties using change notifications
Step 1 Determine Base Value
Applies a precedence order for property providers
Step 2 Evaluate
Evaluate expressions from step 1
Step 3 Apply Animations
Apply animation values to current properties

12. Support for Multiple Providers
Step 4 Coerce
Passes the resulting property values to a CoerceValueCallback delegate
Step 5 Validate
Passes the coerced property values to a ValidateValueCallback delegate

13. Attached Properties
Attached Properties are special dependency properties assigned to arbitrary objects
Objects that don’t have a dependency property of it’s own can be attached and used for property value inheritance
Ex. Assigning a FontSize to a StackPanel

14. Routed Events
Routed Events traverse thru visual and logical trees without the need for custom code
Provides the service of encapsulation of application from visual trees
Allows for embedded complex content and visual trees

15. A Routed Event Implementation
Routed Events are static public fields
Routed Events are represented by RoutedEvents
Created by calling EventManger.RegisterRoutedEvent

16. Routing Strategies & Event Handlers
RoutingStrategy enumeration: Tunneling, Bubbling, Direct
Tunneling raises the routed event at the root then to each element toward the source element
Bubbling raises the routed event at the source element then to each element toward the root
Direct raises the routed event at the source element only

17. Routing Strategies & Event Handlers
Routed Event handlers are similar to .NET event handlers
1st Parameter is System.Object sender
2nd Parameter is RoutedEventArgs e
RoutedEventArgs derived from EventArgs

18. Routed Events in Action
UIElement class defines routed events for keyboard, mouse, stylus input
Many of the bubbling events are paired with tunneling events
Naming convention of tunneling events are prefixed with Preview
Tunneling Event: PreviewMouseMove
Bubbling Event: MouseMove
Event pairing provides the option of canceling or modifying a bubbling event

19. Attached Events
Attached Events provide tunneling and bubbling of routed events to elements that don’t define the event
Similar to attached properties
Routed events can be used as attached events

20. Commands Commands represent independent actions from the UI
Multiple commands can be exposed with the use of events
WPF reduces the amount of code needed to support commands
WPF provides flexibility to change UIs supporting commands without breaking back-end logic

21. Built-In Commands WPF defines many commands ready for use
ApplicationCommands: Cut, Paste
ComponentCommands: MoveUp, MoveDown
MediaCommands: ChannelUp, ChannelDown
NavigationCommands: Search, Refresh
EditingCommands: AlignLeft, AlignCenter
These commands are instances of RoutedUICommand
Implements ICommand & Supports Bubbling

22. Executing Commands w/ Input Gestures
Input Gestures can be bound to commands by adding a KeyBinding or MouseBinding to the elements InputBindings collection
Ex Help command provides auto binding to keyboard shortcuts
Default: F1 Key
Input Gestures can assign F2 key to execute Help command

23. Controls w/ Built-In Command Bindings
Some controls in WPF have their own command bindings
Ex TextBox control bound to Cut, Paste
Built-In Commands can be bound by WPF controls
Button bound to a TextBox Built-In command
WPF’s built-in commands becomes important
Buttons and TextBoxes can gain rich interaction

24. A Tour of the Class Hierarchy

25. Conclusion
We learned the major WPF applications for the .NET Framework
Reviewed types of properties, types of events, trees, declarative code, procedural code
We now have an understanding of WPF controls and developing WPF UIs.

26. References
“Windows Presentation Foundation Unleashed”, Adam Nathan with Daniel Lehenbauer
Software Requirements
Windows that support .NET 3.0: XP SP2, Vista
.NET Framework 3.0
Software Recommended
Windows SDK (
Visual Studio 2005 or later