XAML：在一个DataTemplate绑定属性 [英] XAML: Binding a property in a DataTemplate
问题描述
我是相当新的XAML而是享受学习它。事情我真的是一个DataTemplate一个属性绑定到一个元素中挣扎。
I'm fairly new to XAML but enjoying learning it. The thing I'm really struggling with is binding a property to an element in a DataTemplate.
我创建了一个简单的WPF例子，（希望）解释我的问题。
I have created a simple WPF example to, (hopefully,) explain my problem.
我这个例子，我想在一个DataTemplate复选框的可见性属性绑定到我的视图模型中的财产。 （纯粹使用此方案学习/演示。）
I this example I am trying to bind the Visibility property of a checkbox in a datatemplate to a Property in my view model. (Using this scenario purely for learning/demo.)
我有一个名为'项目'简单的DataModel，但无关紧要在这个例子中。
I have a simple DataModel named 'Item', but is of little relevance in this example.
class Item : INotifyPropertyChanged
{
// Fields...
private bool _IsRequired;
private string _ItemName;
和一个名为ItemViewModel一个相当简单的视图模型。
And a fairly simple View Model named ItemViewModel.
class ItemViewModel : INotifyPropertyChanged
{
private ObservableCollection<Item> _Items;
private bool _IsCheckBoxChecked;
private bool _IsCheckBoxVisible;
public ObservableCollection<Item> Items
{
get { return _Items; }
set { _Items = value; }
}
public bool IsCheckBoxChecked
{
get { return _IsCheckBoxChecked; }
set
{
if (_IsCheckBoxChecked == value)
return;
_IsCheckBoxChecked = value;
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("IsCheckBoxChecked"));
PropertyChanged(this, new PropertyChangedEventArgs("IsCheckBoxVisible"));
}
}
}
public bool IsCheckBoxVisible
{
get { return !_IsCheckBoxChecked; }
set
{
if (_IsCheckBoxVisible == value)
return;
_IsCheckBoxVisible = value;
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("IsCheckBoxVisible"));
}
（构造函数和INotifyPropertyChanged的实施为简洁起见省略。）
(Constructors and INotifyPropertyChanged implementation omitted for brevity.)
在控制奠定MainPage.xaml中进行如下：
Controls laid out in MainPage.xaml as follows.
<Window.Resources>
<local:VisibilityConverter x:Key="VisibilityConverter"/>
</Window.Resources>
<Window.DataContext>
<local:ItemViewModel/>
</Window.DataContext>
<Grid>
<StackPanel>
<CheckBox x:Name="checkBox" Content="Hide CheckBoxes" FontSize="14" IsChecked="{Binding IsCheckBoxChecked, Mode=TwoWay}" />
<ListView ItemsSource="{Binding Items}" HorizontalContentAlignment="Stretch" >
<ListView.ItemTemplate >
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding ItemName}"/>
<CheckBox Grid.Column="1" Visibility="{Binding IsCheckBoxVisible, Converter={StaticResource VisibilityConverter}}" >
<CheckBox.DataContext>
<local:ItemViewModel/>
</CheckBox.DataContext>
</CheckBox>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<StackPanel Orientation="Horizontal" Margin="4,4,0,0">
<TextBlock Text="IsCheckBoxVisible:"/>
<TextBlock Text="{Binding IsCheckBoxVisible}" Margin="4,0,0,0" FontWeight="Bold" />
</StackPanel >
<Button Content="Button" Visibility="{Binding IsCheckBoxVisible, Converter={StaticResource VisibilityConverter}}" Margin="4,4,4,4"/>
</StackPanel>
</Grid>
在'隐藏复选框复选框，势必'IsCheckBoxChecked和用于更新IsCheckBoxVisible。我还添加了几个额外控件的DataTemplate证明下面，（我自己，）的一切工作。）
The 'Hide CheckBoxes' checkbox is bound to 'IsCheckBoxChecked' and is used to update 'IsCheckBoxVisible'. I've also added a couple of extra controls below the DataTemplate to prove, (to myself,) the everything works.)
我也实施了杰夫·威尔考克斯的价值转换器。 （谢谢） http://www.jeff.wilcox.name / 2008/07 /可视性型转换器/
I have also implemented Jeff Wilcox's value converter. (Thank you.) http://www.jeff.wilcox.name/2008/07/visibility-type-converter/
当我运行应用程序，检查和取消选中隐藏复选框，控制的DataTemplate功能外如预期，但是，唉，该数据模板内保持不变。
When I run the app, checking and unchecking the 'Hide Checkbox', controls outside the DataTemplate function as expected but, alas, the inside the data template remains unchanged.
我曾与成功：
IsVisible="{Binding IsChecked, Converter={StaticResource VisibilityConverter}, ElementName=checkBox}"
但我不会只是试图模仿另一个控制，但基于价值作出决策。
But I'm not just trying mimic another control but make decisions based on a value.
我真的AP preciate任何帮助或建议，您可以提供。
I would REALLY appreciate any help or advice you can offer.
感谢您。
推荐答案
当你在一个DataTemplate，你的DataContext是模板对象中的数据，在这种情况下，项目 。因此，在DataTemplate中CheckBox的DataContext的是项目，不是你的 ItemViewModel 。 TextBlock的文本={结合ITEMNAME}/＆GT;你可以通过你的＆LT看到这个，它结合到一个属性上的项目类。绑定到IsCheckBoxVisible正试图找到一个名为IsCheckBoxVisible上项目属性。
When you are in a DataTemplate, your DataContext is the data templated object, in this case an Item. Thus, the DataContext of the CheckBox in the DataTemplate is an Item, not your ItemViewModel. You can see this by your <TextBlock Text="{Binding ItemName}"/>, which binds to a property on the Item class. The Binding to IsCheckBoxVisible is trying to find a property called IsCheckBoxVisible on Item.
有几个办法解决这个，但截至目前为止最简单的就是要做到这一点：
There are a couple of ways around this, but by far the easiest is to do this:
在你的窗口（在XAML），给它和X：名称。例如：
On your Window (in the xaml), give it and x:Name. Eg:
<Window [...blah blah...]
x:Name="MyWindow">
更改绑定是这样的：
Change your binding to look like this:
<CheckBox Grid.Column="1"
Visibility="{Binding DataContext.IsCheckBoxVisible, ElementName=MyWindow, Converter={StaticResource VisibilityConverter}}">
我们正在使用的窗口作为源绑定，然后看着它的DataContext属性（这应该是你的 ItemViewModel ，然后脱下IsCheckBoxVisible财产。
We're using the Window as the source for the Binding, then looking at its DataContext property (which should be your ItemViewModel, and then pulling off the IsCheckBoxVisible property.
另一种选择，如果你想要的东西票友，是使用代理对象引用您的DataContext。见<一href=\"http://weblogs.asp.net/dwahlin/archive/2009/08/20/creating-a-silverlight-datacontext-proxy-to-simplify-data-binding-in-nested-controls.aspx\">this文章DataContextProxy 。
Another option, if you want something fancier, is to use a proxy object to reference your DataContext. See this article on DataContextProxy.
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