Important New Concepts In WPF

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 (http://msdn.com) • Visual Studio 2005 or later