模板化组合框的“默认”文本

I have a combo box that is based on a data template the includes check boxes like such:

我有一个基于数据模板的组合框，包括如下复选框：

    <ComboBox x:Name="cboComplex" Text="Select days...">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal">
                    <CheckBox IsChecked="{Binding Path=IsSelected}" Width="20"/>
                    <TextBlock Text="{Binding DayOfWeek}" Width="100" />
                 </StackPanel>
            </DataTemplate>

        </ComboBox.ItemTemplate>
    </ComboBox>

The problem I'm having is that I'd like the combobox to display "Select days..." and then show the list when clicked. Unfortunately setting the Text property seems to have no effect. Any ideas or help would be greatly appreciated.

我遇到的问题是我希望组合框显示“选择日期......”然后单击时显示列表。不幸的是，设置Text属性似乎没有任何效果。任何想法或帮助将不胜感激。

Thanks in advance!

提前致谢！

Sieg

西格

3 个解决方案

#1

The Text property is used when the ComboBox is editable. You can set a default "Select" type message by adding an element to the ControlTemplate that shows up only when there is no selection and then disappears. Using this method you don't need to worry about modifying your collection or having a user try to pick the "Select" message from the list because it isn't part of the list. I'd recommend using the Tag to set your message on each instance or in a Style and then adding a new TextBlock to display it into the default template:

ComboBox可编辑时使用Text属性。您可以通过向ControlTemplate添加一个元素来设置默认的“选择”类型消息，该元素仅在没有选择时显示，然后消失。使用此方法，您无需担心修改集合或让用户尝试从列表中选择“选择”消息，因为它不是列表的一部分。我建议使用Tag在每个实例或样式中设置消息，然后添加新的TextBlock以将其显示在默认模板中：

<TextBlock x:Name="SelectMessage" HorizontalAlignment="Left" Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Tag}" VerticalAlignment="Center" Margin="{TemplateBinding Padding}" Visibility="Collapsed"/>

Then you could use it like this:

然后你可以像这样使用它：

<ComboBox ItemsSource="{Binding MyList}" Template="{StaticResource ComboBoxMessageTemplate}" Tag="Select days..."/>

Here's a complete Blend generated copy of the default Aero ComboBox template with the changes. You'll also need the theme namespace (xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero") and a reference to the PresentationFramework.Aero assembly:

这是一个完整的Blend生成的默认Aero ComboBox模板副本及其更改。您还需要主题命名空间（xmlns：Microsoft_Windows_Themes =“clr-namespace：Microsoft.Windows.Themes; assembly = PresentationFramework.Aero”）以及对PresentationFramework.Aero程序集的引用：

<Geometry x:Key="DownArrowGeometry">M 0 0 L 3.5 4 L 7 0 Z</Geometry>
<Style x:Key="ComboBoxReadonlyToggleButton" TargetType="{x:Type ToggleButton}">
    <Setter Property="OverridesDefaultStyle" Value="true"/>
    <Setter Property="IsTabStop" Value="false"/>
    <Setter Property="Focusable" Value="false"/>
    <Setter Property="ClickMode" Value="Press"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ToggleButton}">
                <Microsoft_Windows_Themes:ButtonChrome x:Name="Chrome" SnapsToDevicePixels="true" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" RenderMouseOver="{TemplateBinding IsMouseOver}" RenderPressed="{TemplateBinding IsPressed}">
                    <Grid HorizontalAlignment="Right" Width="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}">
                        <Path x:Name="Arrow" Fill="Black" HorizontalAlignment="Center" Margin="3,1,0,0" VerticalAlignment="Center" Data="{StaticResource DownArrowGeometry}"/>
                    </Grid>
                </Microsoft_Windows_Themes:ButtonChrome>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsChecked" Value="true">
                        <Setter Property="RenderPressed" TargetName="Chrome" Value="true"/>
                    </Trigger>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Fill" TargetName="Arrow" Value="#AFAFAF"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

<ControlTemplate x:Key="ComboBoxMessageTemplate" TargetType="{x:Type ComboBox}">
    <Grid x:Name="MainGrid" SnapsToDevicePixels="true">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition MinWidth="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}" Width="0"/>
        </Grid.ColumnDefinitions>
        <Popup x:Name="PART_Popup" Margin="1" AllowsTransparency="true" IsOpen="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}}" Placement="Bottom" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Grid.ColumnSpan="2">
            <Microsoft_Windows_Themes:SystemDropShadowChrome x:Name="Shdw" MaxHeight="{TemplateBinding MaxDropDownHeight}" MinWidth="{Binding ActualWidth, ElementName=MainGrid}" Color="Transparent">
                <Border x:Name="DropDownBorder" Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}" BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" BorderThickness="1">
                    <ScrollViewer CanContentScroll="true">
                        <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" KeyboardNavigation.DirectionalNavigation="Contained"/>
                    </ScrollViewer>
                </Border>
            </Microsoft_Windows_Themes:SystemDropShadowChrome>
        </Popup>
        <ToggleButton Style="{StaticResource ComboBoxReadonlyToggleButton}" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" Grid.ColumnSpan="2" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"/>
        <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" IsHitTestVisible="false" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" Content="{TemplateBinding SelectionBoxItem}" ContentStringFormat="{TemplateBinding SelectionBoxItemStringFormat}" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"/>
        <TextBlock x:Name="SelectMessage" HorizontalAlignment="Left" Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Tag}" VerticalAlignment="Center" Margin="{TemplateBinding Padding}" Visibility="Collapsed"/>
    </Grid>
    <ControlTemplate.Triggers>
        <Trigger Property="SelectedItem" Value="{x:Null}">
            <Setter Property="Visibility" TargetName="SelectMessage" Value="Visible"/>
        </Trigger>
        <Trigger Property="HasDropShadow" SourceName="PART_Popup" Value="true">
            <Setter Property="Margin" TargetName="Shdw" Value="0,0,5,5"/>
            <Setter Property="Color" TargetName="Shdw" Value="#71000000"/>
        </Trigger>
        <Trigger Property="HasItems" Value="false">
            <Setter Property="Height" TargetName="DropDownBorder" Value="95"/>
        </Trigger>
        <Trigger Property="IsEnabled" Value="false">
            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
            <Setter Property="Background" Value="#FFF4F4F4"/>
        </Trigger>
        <Trigger Property="IsGrouping" Value="true">
            <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

#2

Show default text in combo box

在组合框中显示默认文本

 <ComboBox Height="23" HorizontalAlignment="Left" Margin="180,18,0,0" Name="cmbExportData" VerticalAlignment="Top" Width="148" ItemsSource="{Binding}" Text="-- Select Value --" AllowDrop="False" IsEditable="True" IsManipulationEnabled="False" IsReadOnly="True" />

• Set the text property of Combo Box
• 设置组合框的文本属性
• Mark it as IsEditable = true
• 将其标记为IsEditable = true
• Mark it as IsReadOnly = true
• 将其标记为IsReadOnly = true

#3

You will have to create a new Item in your underlying collection class with the value "Select Days...", with index[0] and change the selected index to 0.

您必须在底层集合类中使用值“Select Days ...”在索引[0]中创建一个新项目，并将所选索引更改为0。

    <ComboBox x:Name="cboComplex" SelectedIndex="0">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal">
                    <CheckBox IsChecked="{Binding Path=IsSelected}" Width="20"/>
                    <TextBlock Text="{Binding DayOfWeek}" Width="100" />
                 </StackPanel>
            </DataTemplate>

        </ComboBox.ItemTemplate>
    </ComboBox>

Or the other option is to put a label on top of it with the text "Select Days...", and then listen to OnSelectionChanged event, and if the SelectedIndex is not -1, change the labels visibility to false, otherwise true. e.g.

或者另一个选项是在文本“Select Days ...”上放置一个标签，然后监听OnSelectionChanged事件，如果SelectedIndex不是-1，则将标签可见性更改为false，否则为true。例如

    private void MyListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (MyListBox.SelectedIndex >= 0)
        {
            MyListBoxInitialLabel.Visibility = Visibility.Hidden;
        }
        else
        {
            MyListBoxInitialLabel.Visibility = Visibility.Visible;
        }
    }