自定义附加属性的模板绑定

Question

我正在尝试使用按钮控制中的图像,通过显示不同的图像来动画显示悬停和按下状态.因此,我已经为按钮控件定义了3个附加属性,如下所示.

public class ButtonExtensions : DependencyObject {
    public static DependencyProperty ImageSourceProperty = ...
    public static DependencyProperty ImageHoverSourceProperty = ...
    public static DependencyProperty ImagePressedSourceProperty =
        DependencyProperty.RegisterAttached("ImagePressedSource", typeof(string), typeof(ButtonExtensions));
    public static string GetImagePressedSource(Button target) { return (string)target.GetValue(ImagePressedSourceProperty); }
    public static void SetImagePressedSource(Button target, string value) { target.SetValue(ImagePressedSourceProperty, value); }

我在Button的Style属性设置器中设置了这些属性,如下所示

    <Style x:Key="AddButtonStyle" TargetType="{x:Type Button}" >
        <Setter Property="gs:ButtonExtensions.ImageSource" Value="/HotelReservation.ControlLibrary;component/Images/add-record-icon.png"/>
        <Setter Property="gs:ButtonExtensions.ImageHoverSource" Value="/HotelReservation.ControlLibrary;component/Images/add-record-hover-icon.png"/>
        <Setter Property="gs:ButtonExtensions.ImagePressedSource" Value="/HotelReservation.ControlLibrary;component/Images/add-record-pressed-icon.png"/>

        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Button}">
                    <Grid Height="32" Width="32">
                        <!-- How to use TemplateBinding Here. This does not work -->
                        <Image Name="Normal" Source="{TemplateBinding Property=gs:ButtonExtensions.ImageSource}" />
/>
                        <!-- This Works -->
                        <Image Name="Hover" Source="/HotelReservation.ControlLibrary;component/Images/add-record-hover-icon.png" Opacity="0"/>
                        <Image Name="Pressed" Source="/HotelReservation.ControlLibrary;component/Images/add-record-pressed-icon.png" Opacity="0" />
                    </Grid>
    ...

                </ControlTemplate>

            </Setter.Value>
        </Setter>
    </Style>

如您所见,我正在尝试从Button的控件模板中访问自定义附加属性.我可以得到它的辛勤工作的编码源的属性图像控制,但我wan't使用TemplateBinding代替

Answer 1

使用附加属性作为绑定源需要在属性路径中使用括号.您将不得不使用常规绑定而不是TemplateBinding:

<Image Source="{Binding Path=(gs:ButtonExtensions.ImagePressedSource),
                        RelativeSource={RelativeSource TemplatedParent}}"/>

另请注意,只有在声明附加属性时,才需要从DependencyObject派生ButtonExtensions类.

还建议将DependencyProperty字段声明为只读:

public static readonly DependencyProperty ImagePressedSourceProperty = ...