＃69 wpf基础类提供的功能单元
四个基础的WPF类直接或间接继承自DependencyObject, 提供了超出其基础类的不同功能：
- ContentElement adds (继承自DependencyObject)
- Input events and commanding
- Focus
- Raise and respond to routed events
- Animation support
- FrameworkContentElement adds (继承自ContentElement)
- Additional input elements (e.g. tooltips, context menus)
- Storyboards
- Data binding
- Styles
- Property value inheritance
- UIElement adds (继承自DependencyObject)
- viaVisual
- Hit testing
- Clipping and coordinate transformations
- Participation in visual tree via parent/child relationships
- Layout behavior (measure/arrange)
- Input events and commanding
- Focus
- Raise and respond to routed Events
- Animation support
- FrameworkElement adds (继承自UIElement)
- Additional input elements (e.g. tooltips, context menus)
- Storyboards
- Data binding
- Styles
- Property value inheritance
- Support for the logical tree
#70 另外两个基础类：Freezable和Animatable
在我们的类层次结构中加入另外两个成员：Freezable和Animatable
Freezable - 实现“freezable”机制，对象可以提供一个frozen, read-only的复制。
Animatable - 根据Freeable机制提供给对象实现动画的能力。
#71 将Freezable Objects置为Read-Only State
具有Freeable功能的object一般处于read/write状态，可以被设置为read-only，不能更改的状态（Freeze)。一个被冻结（Frozen)的对象在WPF中是高效的，因为它不需要通知用户改动。
Graphical Object，比如Brushes和3D画图也都继承Freezable，初始化的状态均是Unfrozen。
如果你有一个对象不想进行改动，可使用Freeze方法来将其冻结
// Freeze this object, making it read-only (since we don't plan on changing it) if (theBrush.CanFreeze) theBrush.Freeze();
冻结后如果你还想修改，则会产生InvalidOperationException.
#72 冻结你决定不修改的图形对象
为了更好的性能，最好将一些图像对象（比如Brushes）来进行冻结处理。
代码中冻结的方法：
// SolidColorBrush, created in XAML, not frozen bool frozen = tealBrush.IsFrozen; // frozen = false if (tealBrush.CanFreeze) tealBrush.Freeze(); frozen = tealBrush.IsFrozen; // frozen = true
在Xaml中冻结的方法（要先引入Freeze的命名空间）
<Window x:Class="WpfApplication4.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:po="http://schemas.microsoft.com/winfx/2006/xaml/presentation/options" Title="MainWindow" Height="350" Width="525" > <Window.Resources> <SolidColorBrush x:Key="tealBrush" Color="Teal" po:Freeze="True"/> </Window.Resources>
#73 两种Template
WPF中存在两种Template: ControlTemplate 和 DataTemplate
ControlTemplate样式定义为控件的定制：
<Button Name="btnWithTemplate" Content="Recreate Me" Foreground="Blue"> <Button.Template> <ControlTemplate TargetType="{x:Type Button}"> <StackPanel Orientation="Horizontal"> <Label Content="**" Foreground="{TemplateBinding Foreground}"/> <Button Content="{TemplateBinding Content}" Foreground="{TemplateBinding Foreground}"/> <Label Content="**" Foreground="{TemplateBinding Foreground}"/> </StackPanel> </ControlTemplate> </Button.Template> </Button>
DataTemplate允许你加入数据的Binding，主要是数据决定展现样式：
<Label Name="lblPerson" Content="{Binding}"> <Label.ContentTemplate> <DataTemplate> <Border BorderThickness="2" BorderBrush="DarkBlue"> <StackPanel Orientation="Vertical"> <StackPanel Orientation="Horizontal"> <Label Content="{Binding Path=FirstName}"/> <Label Content="{Binding Path=LastName}" FontWeight="Bold"/> </StackPanel> <Label Content="{Binding Path=BirthYear}" FontStyle="Italic"/> </StackPanel> </Border> </DataTemplate> </Label.ContentTemplate> </Label>
