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。