WPF自定义控件的自定义属性绑定后不更新问题

需要在绑定时设置属性变更触发

UpdateSourceTrigger=PropertyChanged

例如:

<Border CornerRadius="20">
            <Border.Background>
                <ImageBrush 
                    x:Name="objBackImg" 
                    ImageSource="{Binding RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=local:AnimationVideoPlayer},Path=CoverImage,UpdateSourceTrigger=PropertyChanged}"/>
            </Border.Background>
</Border>