WPF:依赖属性的应用

依赖属性与一般属性相比，提供了对资源引用、样式、动画、数据绑定、属性值继承、元数据重载以及WPF设计器的继承支持功能的支持。

下面的这个Demo来自《葵花宝典--WPF自学手册》。

1、MainWindow.xaml

 <Window x:Class="WpfApplication1.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:sys="clr-namespace:System;assembly=mscorlib"
         xmlns:local="clr-namespace:WpfApplication1"
         Title="MainWindow" Height="350" Width="525">
     <Window.Resources>
         <SolidColorBrush x:Key="MyBrush" Color="Gold"/>
         <Style x:Key="GreenButtonStyle">
             <Setter Property="Control.Background" Value="Green"/>
         </Style>
         <local:BindingData x:Key="myDataSource">

         </local:BindingData>
     </Window.Resources>
     <Grid>
         <Grid.RowDefinitions>
             <RowDefinition/>
             <RowDefinition/>
             <RowDefinition/>
         </Grid.RowDefinitions>
         <Grid.ColumnDefinitions>
             <ColumnDefinition/>
             <ColumnDefinition/>
             <ColumnDefinition/>
             <ColumnDefinition/>
         </Grid.ColumnDefinitions>

         <Label HorizontalAlignment="Center" VerticalAlignment="Center">
             资源支持
         </Label>
         <!--金色按钮的背景属性引用了画刷资源-->
         <Button Grid.Row="0" Grid.Column="1" Name="resourceBtn" Background="{DynamicResource MyBrush}">
             金色按钮
         </Button>
         <Label Grid.Row="0" Grid.Column="2" HorizontalAlignment="Center" VerticalAlignment="Center">
             样式支持
         </Label>
         <!--绿色按钮的Style属性引用了样式资源 -->
         <Button Grid.Row="0" Grid.Column="3" Name="typeBtn" Style="{StaticResource GreenButtonStyle}">
             绿色按钮
         </Button>
         <Label Grid.Row="1" Grid.Column="0" HorizontalAlignment="Center" VerticalAlignment="Center">
             动画支持
         </Label>
         <!--动画按钮的背景属性支持动画-->
         <Button Grid.Row="1" Grid.Column="1" Name="animationBtn">
             动画按钮
             <Button.Background>
                 <SolidColorBrush x:Name="AnimBrush"/>
             </Button.Background>
             <Button.Triggers>
                 <EventTrigger RoutedEvent="Button.Loaded">
                     <BeginStoryboard>
                         <Storyboard>
                             <ColorAnimation Storyboard.TargetName="AnimBrush"
                                             Storyboard.TargetProperty="(SolidColorBrush.Color)"
                                             From="Red" To="Green" Duration="0:0:5"
                                             AutoReverse="True" RepeatBehavior="Forever"/>
                         </Storyboard>
                     </BeginStoryboard>
                 </EventTrigger>
             </Button.Triggers>
         </Button>
         <Label Grid.Row="1" Grid.Column="2" HorizontalAlignment="Center" VerticalAlignment="Center">
             数据绑定支持
         </Label>
         <!--按钮对绑定数据的支持-->
         <Button Grid.Row="1" Grid.Column="3" Name="bindingBtn" Background="{Binding Source={StaticResource myDataSource},Path=ColorName}">
             被绑定为红色!
         </Button>
         <!--依赖属性改变相应元素的字体大小-->
         <Label Grid.Row="2" Grid.Column="0" HorizontalAlignment="Center" VerticalAlignment="Center">
             属性继承支持
         </Label>
         <Button Grid.Row="2" Grid.Column="1" Name="FontSizeWinBtn" Click="FontSizeWinBtn_Click">
             设置窗口字体:16
         </Button>
         <Button Grid.Row="2" Grid.Column="2" Name="FontSizeBtn" Click="FontSizeBtn_Click">
             设置按钮字体:8
         </Button>
         <Button Grid.Row="2" Grid.Column="3" Name="ResetFontSizeBtn" Click="ResetFontSizeBtn_Click">
             重置窗口字体:12
         </Button>
     </Grid>

 </Window>

2、BindingData.cs

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;

 namespace WpfApplication1
 {
     class BindingData
     {
         public BindingData()
         {
             ColorName = "Red";
         }

         private string name = "Red";
         public string ColorName
         {
             get { return name; }
             set
             {
                 name = value;

             }
         }
     }
 }

3、MainWindow.xaml.cs

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Data;
 using System.Windows.Documents;
 using System.Windows.Input;
 using System.Windows.Media;
 using System.Windows.Media.Imaging;
 using System.Windows.Navigation;
 using System.Windows.Shapes;

 namespace WpfApplication1
 {
     /// <summary>
     /// Interaction logic for MainWindow.xaml
     /// </summary>
     public partial class MainWindow : Window
     {
         private double _oldFontSize = 0;
         public MainWindow()
         {
             InitializeComponent();

             _oldFontSize = FontSize;
         }
         //改变窗体所有元素的字体大小
         private void FontSizeWinBtn_Click(object sender, RoutedEventArgs e)
         {
             FontSize = 16;
         }
         //仅改变该按钮的字体大小
         private void FontSizeBtn_Click(object sender, RoutedEventArgs e)
         {
             this.FontSizeBtn.FontSize = 8;
         }
         //恢复字体大小
         private void ResetFontSizeBtn_Click(object sender, RoutedEventArgs e)
         {
             FontSize = _oldFontSize;
             this.FontSizeBtn.FontSize = _oldFontSize;
         }

     }
 }

4、运行结果

注意，

在第一次点击“设置窗口字体:16”的按钮时，窗口内所有字体都变成了16号大小的字体，因为这时，窗口内的元素都没有设置过FontSize这个属性，所以继承了窗口的FontSize属性值;

点击"设置按钮字体:8"按钮时，只有该按钮的字体变成8号，因为事件处理函数中只对它的FontSize属性赋值(this.FoniSizeBtn.FontSize=8;)。

之后，再次点击“设置窗口字体:16”的按钮时，"设置按钮字体:8"按钮的字体不会随之变成16号字体，因为该按钮的FontSize属性已经赋值过了，它就不再继承使用窗口的FontSize属性值了。