.net - 绑定(bind)到 DataContext 属性的附加属性

Question

我有一个这样的 AttachedProperty:

Public Class AttachedProperties
    Public Shared ReadOnly IconProperty As DependencyProperty = DependencyProperty.RegisterAttached("Icon", GetType(ImageBrush), GetType(AttachedProperties), New FrameworkPropertyMetadata(Nothing, FrameworkPropertyMetadataOptions.AffectsRender))

    Public Shared Sub SetIcon(ByVal element As Object, ByVal value As ImageBrush)
        element.SetValue(IconProperty, value)
    End Sub

    Public Shared Function GetIcon(ByVal element As Object) As ImageBrush
        Return CType(element.GetValue(IconProperty), ImageBrush)
    End Function
End Class

像这样的 ViewModel:

Public Class ViewModel
    Public Property ShowingPage as Page

    Public Sub New()
        ShowingPage = New SamplePage()
    End Sub
End Class

而我的 SamplePage是这样的:

<Page
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Class="SamplePage">
    <local:AttachedProperties.Icon>
        <ImageBrush Source="Pack://..." /> <!-- Page's Icon -->
    </local:AttachedProperties.Icon>
</Page>

最后我有一个使用 ViewModel 的 View 对象作为 ViewModel:

<Window 
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        x:Class="MainWindow">

        <StackPanel>
            <!-- Showing Icon of page-->
            <Image Source="{Binding (AttachedProperties.Icon), Source=<<ShowingPage>>}" />

            <!-- Showing content of page -->
            <Frame Content="{Binding ShowingPage}" />
        </StackPanel>
    </Window>

问题是 我应该写什么而不是 <<ShowingPage>>显示页面的图标？ 或者是否可以绑定(bind)到 DataContext 上的属性的附加属性?

Answer 1

附加属性有一个基于所有者设置或获取的所有者，返回该所有者的唯一值，因此您必须绑定(bind)到相关的页面控件，然后引用自己的附加属性:

<Image Source="{Binding Path=ShowingPage.(local:AttachedProperties.Icon)}" />

Binding to AttchedProperty