更改自定义属性不会触发绑定更新

我尝试创建一个名为MyComboBox的自定义组合框。它有一个在上一项和下一项之间切换的按钮。

我将底色存储在BaseBackground中。这是有用的，因为我不希望FrontGlyph从模板化的父级继承Background。

<Style x:Key="{x:Type local:MyComboBox}" TargetType="{x:Type local:MyComboBox}">
    </Style.Resources>
    <Setter Property="Focusable" Value="False" />
    <Setter Property="SnapsToDevicePixels" Value="True" />
    <Setter Property="OverridesDefaultStyle" Value="True" />
    <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
    <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
    <Setter Property="ScrollViewer.CanContentScroll" Value="true" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type local:MyComboBox}">
                <Grid Cursor="Hand">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />       <!-- A glyph will come here -->
                        <ColumnDefinition Width="*" />          <!-- The base combo box can take as much space as it can. -->
                    </Grid.ColumnDefinitions>
                    <Path x:Name="FrontGlyph" Grid.Column="0" Data="M 0.0 16.0 L 6.0 0.0 L 6.0 16.0 Z" Fill="{TemplateBinding BaseBackground}" Stretch="Fill" />
                    <Grid x:Name="BaseComboBox" Grid.Column="1" Background="{TemplateBinding BaseBackground}">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto" />   <!-- Previous item -->
                            <ColumnDefinition Width="Auto" />   <!-- Next item -->
                            <ColumnDefinition Width="*" />      <!-- Content Presenter -->
                            <ColumnDefinition Width="Auto" />   <!-- Drop down button -->
                        </Grid.ColumnDefinitions>
                        <Button x:Name="Prev" Grid.Column="0" Background="{TemplateBinding Background}" Style="{StaticResource MyUIButton}">
                            <Path VerticalAlignment="Center" Data="M 4.5 0.5 L 0.5 4.5 L 4.5 8.5 Z" Fill="Black" />
                        </Button>
                        <Button x:Name="Next" Grid.Column="1" Background="{TemplateBinding Background}" Style="{StaticResource MyUIButton}">
                            <Path VerticalAlignment="Center" Data="M 0.5 0.5 L 4.5 4.5 L 0.5 8.5 Z" Fill="Black" />
                        </Button>
                        <ContentPresenter x:Name="ContentSite" Grid.Column="2" IsHitTestVisible="False" Content="{TemplateBinding SelectionBoxItem}" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}" VerticalAlignment="Stretch" HorizontalAlignment="Left" />
                        <ToggleButton x:Name="ToggleButton" Template="{StaticResource ComboBoxToggleButton}" Grid.Column="3" Focusable="false" ClickMode="Press" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Background="{TemplateBinding Background}" />
                        <Popup x:Name="Popup" Placement="Bottom" IsOpen="{TemplateBinding IsDropDownOpen}" AllowsTransparency="True" Focusable="False" PopupAnimation="Slide">
                            <Grid x:Name="DropDown" SnapsToDevicePixels="True" MinWidth="{TemplateBinding ActualWidth}" MaxHeight="{TemplateBinding MaxDropDownHeight}">
                                <Border x:Name="DropDownBorder" BorderThickness="1" BorderBrush="{TemplateBinding Background, Converter={StaticResource LightenBrushColor}, ConverterParameter=0.5}" Background="{TemplateBinding Background}" />
                                <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
                                    <StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained" />
                                </ScrollViewer>
                            </Grid>
                        </Popup>
                    </Grid>
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsMouseOver" Value="True">
                        <Setter Property="BaseBackground" Value="Goldenrod" />  <!-- This does not work -->
                        <!--<Setter TargetName="FrontGlyph" Property="Fill" Value="Goldenrod" />
                        <Setter TargetName="BaseComboBox" Property="Background" Value="{Binding Path=Fill, ElementName=FrontGlyph}" />-->   <!-- These 2 lines do work. -->
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

MyComboBox的源代码:

class MyComboBox : ComboBox
{
    public static readonly DependencyProperty BaseBackgroundProperty;
    public SolidColorBrush BaseBackground { get { return (SolidColorBrush)GetValue(BaseBackgroundProperty); } set { SetValue(BaseBackgroundProperty, value); } }
    static MyComboBox()
    {
        BaseBackgroundProperty = DependencyProperty.Register("BaseBackground", typeof(SolidColorBrush), typeof(MyComboBox), new FrameworkPropertyMetadata(Brushes.Lime, FrameworkPropertyMetadataOptions.AffectsRender, OnBaseBackgroundPropertyChanged));
    }
    public MyComboBox()
    {
        DefaultStyleKey = typeof(MyComboBox);
    }
    private static void OnBaseBackgroundPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
    {
        // This is not called when the trigger tries to set BaseBackground when the mouse is over the control
    }
}

当我将鼠标悬停在控件上时，它应该改变颜色。我应该能够通过改变BaseBackground来做到这一点，因为FrontGlyph和BaseComboBox都有它们的背景色绑定在那里。尽管如此，代码可以编译，但更改并没有发生。不仅在UI上，而且如果我调试代码，我也看不到c#中的变化。

如果我改变FrontGlyph的背景颜色，并将BaseComboBox.BackgroundColor绑定到它，它会很好地工作。

有人能解释为什么我的自定义属性BaseBackground的变化没有注册?它一定不是标准的"实现INotifyPropertyChanged接口"问题，因为我使用Brush作为我的属性，画笔在其他地方工作得很好。:)

我的实现可能看起来很傻。嗯，我对WPF有点陌生。另外，我不想让您负担整个实现，只是试图复制关键部分。

我发现，在我的源代码我设置BaseBackground = new SolidColorBrush(...)，如果一些条件得到满足。如果我删除这行代码，现在触发器工作，BaseBackground被分配为Goldenrod颜色。

但是我想知道，为什么从c#代码更改DependencyProperty会阻止它从XAML标记工作。此外，我需要他们两个都工作。

谢谢。