在Silverlight的列表框中访问父数据上下文 [英] Access parent datacontext in listbox in Silverlight

问题描述

在Silverlight 2中，我使用了一个用户控件，该控件继承了其嵌入页面的数据上下文.该数据上下文包含问题文本，问题类型和答案集合.在用户控件中是一个列表框，该列表框绑定到答案集合.如下图所示:

In Silverlight 2 I'm using a usercontrol which inherits the datacontext of the page that it's embedded on. This datacontext contains question text, a question type and a collection of answers. In the user control is a listbox which is bound to the collection of answers. As shown below:

<ListBox DataContext="{Binding}" x:Name="AnswerListBox" ItemContainerStyle="{StaticResource QuestionStyle}" Grid.Row="1" Width="Auto" Grid.Column="2" ItemsSource="{Binding Path=AnswerList}" BorderBrush="{x:Null}" />       

此列表框具有关联的样式，以单选按钮或复选框的形式显示答案(我想根据问题类型将其隐藏或显示)为:

This listbox has an associated style to display the answers in the form of radio buttons or checkboxes (which I would like to hide or show depending on the question type) as:

<Style TargetType="ListBoxItem" x:Key="QuestionStyle">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="ListBoxItem">                      
                        <StackPanel Background="Transparent" >
                            <RadioButton Visibility="{Binding Path=QuestionType, Converter={StaticResource QuestionTypeConverter}, ConverterParameter='RadioButtonStyle'}" Height="auto" Margin="0,0,0,10"  IsChecked="{TemplateBinding IsSelected}" IsHitTestVisible="False" Content="{Binding Path=AnswerText}">
                            </RadioButton>
                            <CheckBox Visibility="{Binding Path=QuestionType, Converter={StaticResource QuestionTypeConverter}, ConverterParameter='CheckBoxStyle'}" Height="auto" Margin="0,0,0,10" Content="{Binding Path=AnswerText}">
                            </CheckBox>
                        </StackPanel>                                                
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

然后我的问题是:如何访问父数据上下文以获取QuestionType(因为这是用户控件数据上下文本身的属性，而不是AnswerList中AnswerItem的属性)?

So my question is then: how do you access the parent data context in order to get the QuestionType (as this is a property on the user control datacontext itself, not a property on an AnswerItem in the AnswerList)?

或者有更好的方法根据绑定值在xaml中动态切换样式吗?

Alternatively is there a better way to switch styles dynamically in the xaml based on a binding value?

推荐答案

在Silverlight 3和更高版本中，可以使用元素到元素"绑定并指向控件DataContext，然后指向我的示例中的阈值"属性.

In Silverlight 3 and higher you can use Element to Element binding and point to the controls DataContext and then some property in my example its Threshold property.

因此，请为您的控件命名(例如，在我的示例中为x:Name ="control")

So first name your control (for example in my example its x:Name="control")

<UserControl x:Class="SomeApp.Views.MainPageView" x:Name="control" >

然后在列表框ItemTemplate中的此控件内，您可以像这样访问父DataContext:

then inside this control in your ListBox ItemTemplate you can access parent DataContext like this:

    <ListBox ItemsSource="{Binding Path=SomeItems}" >
        <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
            <TextBlock Text="{Binding ElementName=control, Path=DataContext.Threshold}"/>
            </StackPanel>
        </DataTemplate>
       </ListBox.ItemTemplate>         
       </ListBox>

这篇关于在Silverlight的列表框中访问父数据上下文的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！