依赖属性聚集在单独的类中

Question

我的问题涉及 Silverlight（但我猜 WPF 也是如此）。

基本上我知道如何在用户控件中创建依赖属性以及如何使其工作。但我试图做但没有成功的是：在类中创建依赖属性（或多个），并且该类将成为我的用户控件的依赖属性。

换句话说：

// my UserControl
public class DPTest : UserControl
{
    // dependency property, which type is a class, and this class will be holding other dependency properties        
    public static readonly DependencyProperty GroupProperty =
        DependencyProperty.Register("Group", typeof(DPGroup), typeof(DPTest), new PropertyMetadata(new DPGroup(), OnPropertyChanged));

    public DPGroup Group
    {
        get { return (DPGroup)GetValue(GroupProperty); }
        set { SetValue(GroupProperty, value); }
    }    

    // this occurs only when property Group will change, but not when a member of property Group will change        
    static void OnPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        DPTest g = d as DPTest;
        // etc.     
    }
}

// a class, where I want to hold my dependency properties
public class DPGroup : DependencyObject
{

    public static readonly DependencyProperty MyProperty1Property =
        DependencyProperty.RegisterAttached("MyProperty1", typeof(int), typeof(DPGroup), new PropertyMetadata(1, OnPropertyChanged));

    public int MyProperty1
    {
        get { return (int)GetValue(MyProperty1Property); }
        set { SetValue(MyProperty1Property, value); }
    }

    // I would like to notify "the parent" (which means user control "DPTest" ), that member MyProperty1 has changed
    static void OnPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        DPTest g = d as DPTest;
        if (g != null) g.textBox1.Text = g.Group.MyProperty1.ToString();
    }
}

我想要实现的是通知（在XAML中的设计时）用户控件DPTest，即Group属性的成员（Group.MyProperty1）更改了它的值。我设法使其在运行时发生，例如通过使用 DPGroup 类中定义的事件处理程序，但这在 xaml 的设计时不起作用。

<Grid x:Name="LayoutRoot" Background="White">
    <local:DPTest>
        <local:DPTest.Group>
            <local:DPGroup MyProperty1="2"/>
        </local:DPTest.Group>
    </local:DPTest>
</Grid>

它可以工作，但只是第一次，在创建标记期间：

 <local:DPGroup MyProperty1="2"/>

此后，更改 MyProperty1 的值，不会触发 DPTest.OnPropertyChange。可能会触发DBGroup.OnPropertyChanged，但这当然不会通知用户控件DPTest。 那么如何让 DPTest 知道 Group.MyProperty1 已更改？

我不想从 MyProperty1 进行任何绑定 到用户控件 DPTest 内创建的各个属性（不要重复属性），重点是在单独的类中拥有一组属性，因此我可以多次使用该组，例如:

// my UserControl
public class DPTest : UserControl
{
    public DPGroup Group1 { ... } 
    public DPGroup Group2 { ... } 
}

我看到一些类比UIElement.RenderTransform （假设它是我的 Group 属性），例如 ScaleTransform

<Grid x:Name="LayoutRoot" Background="White">
    <Grid.RenderTransform>
        <ScaleTransform ScaleX="0.4"/>
    </Grid.RenderTransform>      
</Grid>

ScaleX 是一个类比MyProperty1。 不同之处在于，改变 ScaleX 的值（在 XAML 中）将反映设计时的立即变化，而这正是我想要实现的。

我试图找到整个谷歌/堆栈溢出和其他问题的解决方案，但没有找到。到处都是在用户控件内创建依赖属性的示例。

感谢您抽出时间。 非常感谢任何帮助。

编辑：根据 Harlow Burgess 的回答，成功地在 Silverlight 中制作了一个工作示例。我将整个解决方案作为单独的答案放在下面。

Answer 1

来自： http://msdn.microsoft.com/en-us/library /ms752914.aspx#setting_properties_data_binding

依赖属性或 DependencyObject 类，本身并不
支持 INotifyPropertyChanged 来生成通知
数据绑定的 DependencyObject 源属性值的更改次数
运营。有关如何创建使用属性的更多信息
在可以报告数据绑定目标更改的数据绑定中，请参阅
数据绑定概述。

设计一个在任何子属性（任何子属性、任何子属性……）的任何属性发生变化时通知整个对象图的系统是低效的。因此，当您需要在属性更改时执行某些操作时，或者如果您确实希望在任何子属性更改时收到通知，则应该使用数据绑定到特定属性，您应该实现INotifyPropertyChanged。

如何：实现属性更改通知

示例：

public class DPGroup : DependencyObject, INotifyPropertyChanged 
{      
    public static readonly DependencyProperty MyProperty1Property =
        DependencyProperty.RegisterAttached(
        "MyProperty1",
        typeof(int),
        typeof(DPGroup),
        new PropertyMetadata(1));

    public int MyProperty1
    {        
        get { return (int)GetValue(MyProperty1Property); }        
        set { SetValue(MyProperty1Property, value); }
    } 

    protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
    {
        base.OnPropertyChanged(e);
        NotifyPropertyChanged(e.Property.Name);
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

public class DPTest : UserControl   
{     
    public static readonly DependencyProperty GroupProperty =         
        DependencyProperty.Register(
        "Group",
        typeof(DPGroup),
        typeof(DPTest),
        new PropertyMetadata(
            new DPGroup(),
            new PropertyChangedCallback(OnGroupPropertyChanged)
            )
        );

    public DPGroup Group     
    {
        get { return (DPGroup)GetValue(GroupProperty); }
        set { SetValue(GroupProperty, value);}     
    }

    static void OnGroupPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        DPTest control = (DPTest)d;

        DPGroup oldGroup = e.OldValue as DPGroup;
        if (oldGroup != null)
        {
            oldGroup.PropertyChanged -=new PropertyChangedEventHandler(control.group_PropertyChanged);
        }

        DPGroup newGroup = e.NewValue as DPGroup;
        if (newGroup != null)
        {
            newGroup.PropertyChanged +=new PropertyChangedEventHandler(control.group_PropertyChanged);
        }

        control.UpdateTextBox();
    }

    private void group_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        this.UpdateTextBox();
    }

    private void UpdateTextBox()
    {
        this.textBox1.Text = this.Group.MyProperty1.ToString(); 
    }

    private TextBox textBox1;

}  

Answer 2

好的，根据 @Harlow Burgess 的回答，我成功地在 Silverlight 中制作了一个工作示例。

基本上区别在于，在 SL 中，DependencyObject 类没有 OnPropertyChanged 方法，因此在 DPGroup 类中我们无法重写它，但我们可以附加它此方法以另一种方式，通过：

new PropertyMetadata(1, OnPropertyChanged).

因此 DPGroup 类将如下所示：

public class DPGroup : DependencyObject, INotifyPropertyChanged
{
    public static readonly DependencyProperty MyProperty1Property =
        DependencyProperty.RegisterAttached(
        "MyProperty1",
        typeof(int),
        typeof(DPGroup),
        new PropertyMetadata(1, OnPropertyChanged));

    public int MyProperty1
    {
        get { return (int)GetValue(MyProperty1Property); }
        set { SetValue(MyProperty1Property, value); }
    }   

    // static method invoked when MyProperty1 has changed value
    static void OnPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        DPGroup g = d as DPGroup;
        if (g != null)
        {
            g.MyProperty1 = (int)e.NewValue;
            // invoking event handler, to notify parent class about changed value of DP
            if (g.PropertyChanged != null) g.PropertyChanged(g, null);                
        }
    }

    // event handler, for use in parent class
    public event PropertyChangedEventHandler PropertyChanged;             
}

父类，包含类型 DPGroup 的依赖属性：

public partial class DPTest : UserControl
{
    public static readonly DependencyProperty GroupProperty =
        DependencyProperty.Register(
        "Group",
        typeof(DPGroup),
        typeof(DPTest),
        new PropertyMetadata(
            new DPGroup(),
            new PropertyChangedCallback(OnGroupPropertyChanged)
            )
        );

    public DPGroup Group
    {
        get { return (DPGroup)GetValue(GroupProperty); }
        set { SetValue(GroupProperty, value); }
    }

    // static method invoked when Group property has changed value
    // here we need to attach event handler defined if DPGroup, so it will fire from inside Group property, 
    // when Group.MyProperty1 will change value
    static void OnGroupPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        DPTest control = (DPTest)d;

        DPGroup oldGroup = e.OldValue as DPGroup;
        // removing event handler from prevoius instance of DBGroup
        if (oldGroup != null)            
            oldGroup.PropertyChanged -= new PropertyChangedEventHandler(control.group_PropertyChanged);

        DPGroup newGroup = e.NewValue as DPGroup;
        // adding event handler to new instance of DBGroup
        if (newGroup != null)            
            newGroup.PropertyChanged += new PropertyChangedEventHandler(control.group_PropertyChanged);

        DPTest g = d as DPTest;
        if (g != null)
            control.UpdateTextBox();            
    }

    private void group_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        UpdateTextBox();
    }

    // here you can do anything with changed value Group.MyProperty1
    private void UpdateTextBox()
    {
        this.textBox1.Text = this.Group.MyProperty1.ToString();
    }

    public DPTest()
    {
        InitializeComponent();

    }
}  

现在，DPGroup 类的 XAML 部分代码>DPTest：

<UserControl x:Class="Silverlight_Workbench_2.DPTest"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:Silverlight_Workbench_2"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400" >

    <Grid x:Name="LayoutRoot" Background="White">

        <TextBox Height="23" HorizontalAlignment="Left" Margin="76,61,0,0" 
                 x:Name="textBox1" VerticalAlignment="Top" Width="120" />

    </Grid>
</UserControl>

最后，我们可以将 DPTest 嵌入到任何控件的某些内容中，例如嵌入到另一个用户控件的 Grid 中：

<UserControl x:Class="Silverlight_Workbench_2.DPTestMain"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:Silverlight_Workbench_2"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400" xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk">

    <Grid x:Name="LayoutRoot" Background="White">

        <local:DPTest>
            <local:DPTest.Group>
                <!--here we can change value, and it will be reflected in design window
                as a text in textBox1-->
                <local:DPGroup MyProperty1="8"/>
            </local:DPTest.Group>
        </local:DPTest>

    </Grid>
</UserControl>

仅此而已，再次感谢 Harlow Burgess 的帮助！