何时更新复杂路径的绑定目标？

Question

在WPF中使用数据绑定时，当通过INotifyPropertyChanged接口通知目标依赖项对象源已更改时，目标依赖项对象将更新。

例如：

<TextBlock Text="{Binding Path=SomeField}"/>

每当从源调用PropertyChanged(this, new PropertyChangedEventArgs("SomeField"))时，文本字段都会更改以正确反映SomeField的值。

如果我使用如下所示的复杂路径：

<TextBlock Text="{Binding Path=SomeObjField.AnotherField}"/>

文本字段是否会针对源上的PropertyChanged(this, new PropertyChangedEventArgs("SomeObjField"))进行更新？

那么中间对象(包含在SomeObjField中的对象)上的PropertyChanged(this, new PropertyChangedEventArgs("AnotherField"))呢？

源对象和字段不是依赖对象或属性！假设属性/类的实现如下所示：

public class Data : INotifyPropertyChanged
{
   // INotifyPropertyChanged implementation...

   public string SomeField
   {
      get { return val; }
      set
      {
         val = value;
         // fire PropertyChanged()
      }
   }

   public SubData SomeObjField
   {
      get { return val; }
      set
      {
         val = value;
         // fire PropertyChanged()
      }
   }   
}

public class SubData : INotifyPropertyChanged
{
   // INotifyPropertyChanged implementation...

   public string AnotherField
   {
      get { return val; }
      set
      {
         val = value;
         // fire PropertyChanged()
      }
   }
}

Answer 1

经过进一步研究，似乎当复杂路径的任何部分发送更改通知时，绑定都会更新。因此，如果源对象或中间对象被更改，则绑定将被更新。

我构建了一个类似Jared的测试项目：

<StackPanel Name="m_panel">
    <TextBox IsReadOnly="True" Text="{Binding Path=SomeObjField.AnotherField }"  />
    <TextBox x:Name="field1"/>
    <Button Click="Button1_Click">Edit Root Object</Button>
    <TextBox x:Name="field2"/>
    <Button Click="Button2_Click">Edit Sub Object</Button>
</StackPanel>

和后面的代码：

public Window1()
{
    InitializeComponent();
    m_panel.DataContext = new Data();
}

private void Button1_Click(object sender, RoutedEventArgs e)
{
    Data d = m_panel.DataContext as Data;
    d.SomeObjField = new SubData(field1.Text);
}

private void Button2_Click(object sender, RoutedEventArgs e)
{
    Data d = m_panel.DataContext as Data;
    d.SomeObjField.AnotherField = field2.Text;
}

我正在使用我在问题中提供的基本数据实现。

Answer 2

我不是100%确定你在PropertyChanged部分问的是什么。但是，如果涉及的属性都是DependencyProperty支持的属性，那么这应该会按预期工作。我画出了下面的例子

Window1.xaml

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">
    <StackPanel Name="m_panel">
        <TextBlock Text="{Binding Path=SomeField}" />
        <TextBlock Text="{Binding Path=SomeField.AnotherField }"  />
        <Button Click="Button_Click">Update Root Object</Button>
        <Button Click="Button_Click_1">Update Another Field</Button>
    </StackPanel>
</Window>

Window1.xaml.cs

public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();
        m_panel.DataContext = new Class1();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        ((Class1)m_panel.DataContext).SomeField = new Class2();
    }

    private void Button_Click_1(object sender, RoutedEventArgs e)
    {
        ((Class1)m_panel.DataContext).SomeField.AnotherField = "Updated field";
    }
}

以及这些类

public class Class1 : DependencyObject
{
    public static DependencyProperty SomeFieldProperty = DependencyProperty.Register(
        "SomeField",
        typeof(Class2),
        typeof(Class1));

    public Class2 SomeField
    {
        get { return (Class2)GetValue(SomeFieldProperty); }
        set { SetValue(SomeFieldProperty, value); }
    }

    public Class1()
    {
        SomeField = new Class2();
    }
}

public class Class2 : DependencyObject
{
    public static DependencyProperty AnotherFieldProperty = DependencyProperty.Register(
        "AnotherField",
        typeof(string),
        typeof(Class2));

    public string AnotherField
    {
        get { return (string)GetValue(AnotherFieldProperty); }
        set { SetValue(AnotherFieldProperty, value); }
    }

    public Class2()
    {
        AnotherField = "Default Value";
    }
}