问题
I want to reuse a DataTemplate for multiple columns in a ListView. Given the two XmlDataProvider I select values from the second by using the selected item in the first.
This works if I specify the additional resource in the DataTemplate. But this forces me to duplicate the code of the DataTemplate and just exchange the addtional resource.
What I would like to do is this:
<Window x:Class="LayoutTests.Window2"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:LayoutTests"
Title="Window2" Height="300" Width="300">
<Window.Resources>
<XmlDataProvider x:Key="XmlDataA" IsInitialLoadEnabled="True">
<x:XData>
<Items xmlns="">
<Item id="1" text="A:1"/>
<Item id="2" text="A:2"/>
<Item id="3" text="A:3"/>
</Items>
</x:XData>
</XmlDataProvider>
<XmlDataProvider x:Key="XmlDataB" IsInitialLoadEnabled="True">
<x:XData>
<Items xmlns="">
<Item id="1" text="B:1"/>
<Item id="2" text="B:2"/>
<Item id="3" text="B:3"/>
</Items>
</x:XData>
</XmlDataProvider>
<local:MultiXmlConverter x:Key="MultiXmlConverter"/>
<local:DatabindingDebugConverter x:Key="DatabindingDebugConverter"/>
<DataTemplate x:Key="Template" >
<TextBlock Text="{Binding Converter={StaticResource MultiXmlConverter}}"/>
</DataTemplate>
</Window.Resources>
<Grid>
<ListView ItemsSource="{Binding Source={StaticResource XmlDataA}, XPath='/Items/Item'}" Background="Transparent">
<ListView.View>
<GridView>
<GridViewColumn CellTemplate="{StaticResource Template}">
<GridViewColumn.DisplayMemberBinding>
<MultiBinding>
<Binding Path="/"/>
<Binding Source="{StaticResource XmlDataB}"/>
</MultiBinding>
</GridViewColumn.DisplayMemberBinding>
</GridViewColumn>
</GridView>
</ListView.View>
</ListView>
</Grid>
</Window>
For completeness (and reference) here is a possible converter:
public class MultiXmlConverter : IMultiValueConverter
{
public object Convert(object[] value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var element = value[0] as XmlElement;
var dataProvider = value[1] as XmlDataProvider;
XmlNodeList nodes = dataProvider.Document.SelectNodes("/Items/Item/[@id='" + element.Attributes["id"].Value.ToString() + "']");
return nodes[0].Attributes["Text"].Value.ToString();
}
public object[] ConvertBack(object value, Type[] targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new Exception("The method or operation is not implemented.");
}
}
Note that above XAML code will not work and produces the following error: "Cannot set MultiBinding because MultiValueConverter must be specified.". The MultiBinding is merely a placeholder for the thing I want to do. Research didnt reveal any possibility to pass additional parameters to a DataTemplate - but I cant believe that something so usefull is not hidden somewhere.
So how do I pass an additional resource into a DataTemplate next to the DataContext?
回答1:
After a lot of debugging and discussion I found a solution to above problem.
To pass additional data to a template one can attach properties to parent elements in the hierarchy. Unfortunately the thing where we have access - the GridViewColumn isn't showing up in the visual tree. To be able to specify the right resources, we have to wrap things up a little bit. I modified above example to be complete so this is a little bit longer:
<Window x:Class="LayoutTests.Window2"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:LayoutTests"
Title="Window2" Height="300" Width="300">
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary>
<XmlDataProvider x:Key="XmlDataA" IsInitialLoadEnabled="True">
<x:XData>
<Items xmlns="">
<Item id="1" text="A:1"/>
<Item id="2" text="A:2"/>
<Item id="3" text="A:3"/>
</Items>
</x:XData>
</XmlDataProvider>
</ResourceDictionary>
<ResourceDictionary>
<XmlDataProvider x:Key="XmlDataB" IsInitialLoadEnabled="True">
<x:XData>
<Items xmlns="">
<Item id="1" text="B:1"/>
<Item id="2" text="B:2"/>
<Item id="3" text="B:3"/>
</Items>
</x:XData>
</XmlDataProvider>
</ResourceDictionary>
<ResourceDictionary>
<local:MultiXmlConverter x:Key="MultiXmlConverter"/>
<local:DatabindingDebugConverter x:Key="DatabindingDebugConverter"/>
<DataTemplate x:Key="Template" >
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource MultiXmlConverter}">
<Binding/>
<Binding RelativeSource="{RelativeSource TemplatedParent}" Path="(local:Window2.AttachedXmlDataProvider)"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</DataTemplate>
<DataTemplate x:Key="TemplateA">
<ContentPresenter ContentTemplate="{StaticResource Template}" local:Window2.AttachedXmlDataProvider="{StaticResource XmlDataA}"/>
</DataTemplate>
<DataTemplate x:Key="TemplateB">
<ContentPresenter ContentTemplate="{StaticResource Template}" local:Window2.AttachedXmlDataProvider="{StaticResource XmlDataB}"/>
</DataTemplate>
</ResourceDictionary>
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>
<Grid>
<ListView ItemsSource="{Binding Source={StaticResource XmlDataA}, XPath='/Items/Item'}" Background="Transparent">
<ListView.View>
<GridView>
<GridViewColumn CellTemplate="{StaticResource TemplateA}"/>
<GridViewColumn CellTemplate="{StaticResource TemplateB}"/>
</GridView>
</ListView.View>
</ListView>
</Grid>
</Window>
And the stuff from the .cs file:
public partial class Window2 : Window
{
public Window2()
{
InitializeComponent();
}
public static readonly DependencyProperty AttachedXmlDataProviderProperty =
DependencyProperty.RegisterAttached("AttachedXmlDataProvider",
typeof(XmlDataProvider),
typeof(Window2),
new FrameworkPropertyMetadata((XmlDataProvider)null, FrameworkPropertyMetadataOptions.AffectsRender));
public static void SetAttachedXmlDataProvider(DependencyObject depObj, XmlDataProvider value)
{
depObj.SetValue(AttachedXmlDataProviderProperty, value);
}
public static XmlDataProvider GetAttachedXmlDataProvider(DependencyObject depObj)
{
return (XmlDataProvider)depObj.GetValue(AttachedXmlDataProviderProperty);
}
}
public class MultiXmlConverter : IMultiValueConverter
{
public object Convert(object[] value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var element = value[0] as XmlElement;
var dataProvider = value[1] as XmlDataProvider;
string id = element.Attributes["id"].Value.ToString();
if( dataProvider.Document == null )
return null;
XmlNodeList nodes = dataProvider.Document.SelectNodes("/Items/Item[@id='" + id + "']");
string result = nodes[0].Attributes["text"].Value;
return result;
}
public object[] ConvertBack(object value, Type[] targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new Exception("The method or operation is not implemented.");
}
}
The beauty of the code above lies in the fact that we integrate different resources in a DataTemplate and can exchange the resource with only a small amount of code. Namely in writing a DataTemplate that simply wraps up the real template.
It may not be obvious from above example, but if you have a real complicate DataTemplate and need to just change the resources it's working on this is a really nice solution.
来源：https://stackoverflow.com/questions/10210519/is-it-possible-to-pass-multiple-resources-into-a-datatemplate