WPF ControlTemplate:如何为TemplateBinding提供默认值？

Question

我正在编写一个WPF控件,它是Button的子类.然后我在Themes\generic.xaml中提供了一个默认样式,它看起来像这样(简化):

<Style TargetType="{x:Type WPFControls:MyButton}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type WPFControls:MyButton}">
                <Button 
                    x:Name="PART_Button"
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    />
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

我希望用户有机会更改控件的背景,但如果他没有,我想提供默认值.我该怎么做？

当我在发布的代码中执行它时,Background和BorderBrush为null(=不存在),除非用户明确指定它们(这有效地强制用户总是提供一些值),但标准的Windows控件(如Button)提供了默认的外观,仍然可以由用户定制.如何在我的控制下做到这一点？

谢谢!

Michael Morton解决方案:

您可以在样式中提供默认设置:

<Style TargetType="{x:Type TestTemplate:MyButton}">
    <Setter Property="Background" Value="Red" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TestTemplate:MyButton}">
                <Button 
                    x:Name="PART_Button"
                    IsEnabled="{TemplateBinding IsEnabled}"
                    Content="{TemplateBinding Content}"
                    Background="{TemplateBinding Background}"
                    />
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

用法:

<StackPanel>
    <TestTemplate:MyButton Background="Blue">Explicitly blue</TestTemplate:MyButton>
    <TestTemplate:MyButton>Naturally red</TestTemplate:MyButton>
</StackPanel>

Answer 1

您可以在样式上为这两个属性定义setter.

例如,一些一般定义:

<LinearGradientBrush x:Key="ButtonNormalBackground" EndPoint="0,1" StartPoint="0,0">
    <GradientStop Color="#F3F3F3" Offset="0"/>
    <GradientStop Color="#EBEBEB" Offset="0.5"/>
    <GradientStop Color="#DDDDDD" Offset="0.5"/>
    <GradientStop Color="#CDCDCD" Offset="1"/>
</LinearGradientBrush>

<SolidColorBrush x:Key="ButtonNormalBorder" Color="#FF707070"/>

然后,在你的风格定义中:

<Setter Property="Background" Value="{StaticResource ButtonNormalBackground}" />
<Setter Property="BorderBrush" Value="{StaticResource ButtonNormalBorder}" />

Answer 2

<Style TargetType="{x:Type WPFControls:MyButton}">
    <Setter Property="Background" Value="Black">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type WPFControls:MyButton}">
                <Button 
                    x:Name="PART_Button"
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    />
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

注意第二个字符串，我将黑色设置为背景默认值。