WPF Architecture

This Article provides a guided tour of the Windows Presentation Foundation (WPF) class hierarchy.
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This Article provides a guided tour of the Windows Presentation Foundation (WPF) class hierarchy. It covers most of the major subsystems of WPF, and describes how they interact. It also provide informatory details regarding some of the choices made by the architects of WPF.


This Article contains the following sections.

Control's most significant feature is templating. If you think about WPF's composition system as a retained mode rendering system, templating allows a control to describe its rendering in a parameterized, declarative manner. A ControlTemplate is really nothing more than a script to create a set of child elements, with bindings to properties offered by the control.

Control provides a set of stock properties, Foreground, Background, Padding, to name a few, which template authors can then use to customize the display of a control. The implementation of a control provides a data model and interaction model. The interaction model defines a set of commands (like Close for a window) and bindings to input gestures (like clicking the red X in the upper corner of the window). The data model provides a set of properties to either customize the interaction model or customize the display (determined by the template).

This split between the data model (properties), interaction model (commands and events), and display model (templates) enables complete customization of a control's look and behavior.

A common aspect of the data model of controls is the content model. If you look at a control like Button, you will see that it has a property named "Content" of type Object. In Windows Forms and ASP.NET, this property would typically be a string - however that limits the type of content you can put in a button. Content for a button can either be a simple string, a complex data object, or an entire element tree. In the case of a data object, the data template is used to construct a display.

WPF is designed to allow you to create dynamic, data driven presentation systems. Every part of the system is designed to create objects through property sets that drive behavior. Data binding is a fundamental part of the system, and is integrated at every layer.

Traditional applications create a display and then bind to some data. In WPF, everything about the control, every aspect of the display, is generated by some type of data binding. The text found inside a button is displayed by creating a composed control inside of the button and binding its display to the button's content property.

When you begin developing WPF based applications, it should feel very familiar. You can set properties, use objects, and data bind in much the same way that you can using Windows Forms or ASP.NET. With a deeper investigation into the architecture of WPF, you'll find that the possibility exists for creating much richer applications that fundamentally treat data as the core driver of the application.

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