You??™ll learn more about the WPF
threading model in Chapter 3.
System.Windows.DependencyObject
In WPF, the central way of interacting with onscreen elements is through properties. Early on
in the design cycle, the WPF architects decided to create a more powerful property model that
baked in features such as change notification, inherited default values, and more economical
property storage. The ultimate result is the dependency property feature, which you??™ll explore
in Chapter 6. By deriving from DependencyObject, WPF classes get support for dependency
properties.
System.Windows.Media.Visual
Every element that appears in a WPF is, at heart, a Visual. You can think of the Visual class as a
single drawing object, which encapsulates drawing instructions, additional details about how
the drawing should be performed (such as clipping, opacity, and transformation settings), and
basic functionality (such as hit testing). The Visual class also provides the link between the
managed WPF libraries and the milcore.dll that renders your display. Any class that derives
from Visual has the ability to be displayed on a window. If you prefer to create your user interface
using a lightweight API that doesn??™t have the higher-level framework features of WPF, you
can program directly with Visual objects, as described in Chapter 14.
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