WPF：数据绑定滑块值到XAML中的工具提示内容字符串

Question

在基于C＃的WPF UserControl中，我有一组Sliders来调整Color元素的红色，绿色和蓝色值;基本上UserControl是一个颜色选择器。我将ToolTipOpening事件处理程序的XAML和C＃代码组合在一起，允许我设置表示Color组件属性值的单个整数值。因此，如果我将滑块定位为调整滑块中间颜色的红色数量，则工具提示将显示“红色：125”，因为每个颜色组件属性值的范围可以是0到255.代码片段下面的XAML和C＃按预期工作：

XAML：

<UserControl x:Class="CustomColorPicker.ColorPickerUserControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             Name="colorPicker">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="50" />
            <ColumnDefinition Width="175" />
            <ColumnDefinition Width="100" />
        </Grid.ColumnDefinitions>

        <Label HorizontalAlignment="Right">Red:</Label>
        <Slider Grid.Row="0" Grid.Column="1" Name="sliderRed" Minimum="0" Maximum="255"
                Margin="{Binding ElementName=colorPicker, Path=Padding}"
                Value="{Binding ElementName=colorPicker, Path=Red}" 
                ToolTipOpening="OnColorSliderToolTipOpening" 
                ToolTip="Red: 0" />

        <Label Grid.Row="1" Grid.Column="0" HorizontalAlignment="Right">Green:</Label>
        <Slider Grid.Row="1" Grid.Column="1" Name="sliderGreen" Minimum="0" Maximum="255"
                Margin="{Binding ElementName=colorPicker, Path=Padding}"
                Value="{Binding ElementName=colorPicker, Path=Green}" 
                ToolTipOpening="OnColorSliderToolTipOpening" ToolTip="Green: 0" />

        <Label Grid.Row="2" Grid.Column="0" HorizontalAlignment="Right">Blue:</Label>
        <Slider Grid.Row="2" Grid.Column="1" Name="sliderBlue" Minimum="0" Maximum="255"
                Margin="{Binding ElementName=colorPicker, Path=Padding}"
                Value="{Binding ElementName=colorPicker, Path=Blue}" 
                ToolTipOpening="OnColorSliderToolTipOpening" ToolTip="Blue: 0" />

        <Rectangle Grid.Column="2" Grid.RowSpan="3"
                   Margin="{Binding ElementName=colorPicker, Path=Padding}"
                   Width="85" Stroke="Black" StrokeThickness="1">
            <Rectangle.Fill>
                <SolidColorBrush Color="{Binding ElementName=colorPicker, Path=Color}" />
            </Rectangle.Fill>
        </Rectangle>    
    </Grid>
</UserControl>

C＃：

    private void OnColorSliderToolTipOpening(object sender, ToolTipEventArgs e)
    {
        Slider slider = (Slider) sender;

        string colorName = "N/A";
        int colorValue = 0;

        if (slider.Name == "sliderRed")
        {
            colorName = "Red";
            colorValue = (int) Color.R;                
        }

        else if (slider.Name == "sliderGreen")
        {
            colorName = "Green";
            colorValue = (int) Color.G;
        }

        else if (slider.Name == "sliderBlue")
        {
            colorName = "Blue";
            colorValue = (int) Color.B;
        }

        string colorTip =
        string.Format("{0}: {1}", colorName, colorValue.ToString());

        slider.ToolTip = colorTip;

        return;
    }

有没有办法消除背后的代码，并使用 ToolTip.Content 和 工具提示设置工具提示内容以显示相同的字符串。仅限XAML中的ContentStringFormat 属性，允许在C＃后面的代码中消除ToolTipOpening事件处理程序？我使用DataBinding尝试了以下XAML来格式化Slider工具提示的内容字符串：

XAML：

    <Slider Grid.Row="2" Grid.Column="1" Name="sliderBlue" Minimum="0" Maximum="255"
            Margin="{Binding ElementName=colorPicker, Path=Padding}"
            Value="{Binding ElementName=colorPicker, Path=Blue}">
        <Slider.ToolTip>
            <ToolTip
                Content="{Binding ElementName=colorPicker, Path=Blue}"
                ContentStringFormat="{}Blue: {0}" />
        </Slider.ToolTip>
    </Slider>

并且ToolTip Popup显示为空：

Answer 1

每个ElementName的绑定就像RelativeSource与FindAncestor一样不在范围内，因为ToolTip是Popup，它不是VisualTree的一部分（它创造了自己的）。但您可以使用ToolTip.PlacementTarget Property获取Slider控件并捕获值。

<Slider.ToolTip>
    <ToolTip Content="{Binding RelativeSource={RelativeSource Self},
                               Path=PlacementTarget.Value}"
             ContentStringFormat="Blue: {0:0}" />
</Slider.ToolTip>

请注意:0中的额外ContentStringFormat="Blue: {0:0}"以对值进行四舍五入。