将资源绑定到视图模型

问题描述

如何在视图模型中将数据绑定到用户控件的资源中的对象中？这是一个非常抽象的例子：

 < UserControl ... 
 xmlns：local =clr-namespace： My.Local.Namespace
 Name =userControl> 
< UserControl.Resources> 
< local：GroupingProvider x：Key =groupingProviderGroupValue ={Binding ???}/> 
< /UserControl.Resources> 
 
< Grid> 
< local：GroupingConsumer Name =groupingConsumer1Provider = {StaticResource groupingProvider} /> 
< local：GroupingConsumer Name =groupingConsumer2Provider = {StaticResource groupingProvider} /> 
< / Grid> 
< / UserControl> 
  

如何将 GroupValue 绑定到属性在这个观点的视图模型中。我尝试了以下内容：

 < local：GroupingProvider x：Key =groupingProviderGroupValue ={Binding ElementName = userControl，Path = DataContext.Property}/> 
  

但这不行。

编辑：

GroupProvider extends DependencyObject 和 GroupValue 是 DependencyProperty 。我收到以下错误：

  System.Windows.Data错误：2：找不到针对目标元素的FrameworkElement或FrameworkContentElement 。 BindingExpression：Path = DataContext.Property; DataItem = null;目标元素是GroupingProvider（HashCode = 47478197）;目标属性是'GroupValue'（键入'TimeSpan'）
  

这似乎表明它找不到 userControl 。

更多编辑：

$ b $没有人回答我的问题？有没有办法做到这一点？

解决方案

我知道它有点迟了，但我也有同样的问题。 Ricks答案是正确的，您需要继承 Freezable 。

以下代码给出了与您相同的错误得到

不工作资源：

  public class PrintBarcodesDocumentHelper：DependencyObject 
 {
 public IEnumerable< BarcodeResult>条形码
 {
 get {return（IEnumerable< BarcodeResult>）GetValue（BarcodesProperty）; } 
 set {SetValue（BarcodesProperty，value）; 
 
 
 public static readonly DependencyProperty BarcodesProperty = 
 DependencyProperty.Register（条形码，typeof（IEnumerable< BarcodeResult>），typeof（PrintBarcodesDocumentHelper），新的PropertyMetadata（null， HandleBarcodesChanged））; 
 
 private static void HandleBarcodesChanged（DependencyObject d，DependencyPropertyChangedEventArgs e）
 {
 //做东西
} 
} 
  

Xaml：

 < UserControl资源> 
<条形码：PrintBarcodesDocumentHelper x：Key =docHelper条形码={Binding BarcodeResults}/> 
< /UserControl.Resources> 
  

我的viewmodel绑定到 DataContext UserControl 。

错误：

  System.Windows.Data错误：2：找不到针对目标元素的FrameworkElement或FrameworkContentElement。 BindingExpression：Path = BarcodeResults; DataItem = null;目标元素为'PrintBarcodesDocumentHelper'（HashCode = 55335902）;目标属性是'Barcodes'（类型'IEnumerable`1'）
  

工作资源类：

  public class PrintBarcodesDocumentHelper：Freezable 
 {
 //相同的属性
 
 protected override Freezable CreateInstanceCore（）
 {
返回新的PrintBarcodesDocumentHelper（）; 
} 
} 
  

不幸的是，我不知道为什么它必须是一个 Freezable 。

How do you bind data from the view model into an object in the resources of the user control? Here is a very abstract example:

<UserControl ...
             xmlns:local="clr-namespace:My.Local.Namespace"
             Name="userControl">
    <UserControl.Resources>
        <local:GroupingProvider x:Key="groupingProvider" GroupValue="{Binding ???}" />
    </UserControl.Resources>

    <Grid>
        <local:GroupingConsumer Name="groupingConsumer1" Provider={StaticResource groupingProvider"} />
        <local:GroupingConsumer Name="groupingConsumer2" Provider={StaticResource groupingProvider"} />
    </Grid>
</UserControl>

How do I bind GroupValue to a property in the view model behind this view. I've tried the following:

<local:GroupingProvider x:Key="groupingProvider" GroupValue="{Binding ElementName=userControl, Path=DataContext.Property}"/>

But this doesn't work.

Edit:

GroupProvider extends DependencyObject and GroupValue is the name of a DependencyProperty. I'm getting the following error:

System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=DataContext.Property; DataItem=null; target element is 'GroupingProvider' (HashCode=47478197); target property is 'GroupValue' (type 'TimeSpan')

This seems to suggest that it cannot find userControl.

More Edit:

Nobody has an answer to my question? Is there not a way to do this?

解决方案

I know its a bit late, but i had the same problem. Ricks answer is right, you need to inherit from Freezable.

The following Code gave me the same error as you got

Not working resource:

public class PrintBarcodesDocumentHelper : DependencyObject
{
    public IEnumerable<BarcodeResult> Barcodes
    {
        get { return (IEnumerable<BarcodeResult>)GetValue(BarcodesProperty); }
        set { SetValue(BarcodesProperty, value); }
    }

    public static readonly DependencyProperty BarcodesProperty =
        DependencyProperty.Register("Barcodes", typeof(IEnumerable<BarcodeResult>), typeof(PrintBarcodesDocumentHelper), new PropertyMetadata(null, HandleBarcodesChanged));

    private static void HandleBarcodesChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        // Do stuff
    }
}

Xaml:

<UserControl.Resources>
    <Barcodes:PrintBarcodesDocumentHelper x:Key="docHelper" Barcodes="{Binding BarcodeResults}"/>
</UserControl.Resources>

My viewmodel is bound to the DataContext of the UserControl.

Error:

System.Windows.Data Error: 2 : Cannot find governing FrameworkElement or FrameworkContentElement for target element. BindingExpression:Path=BarcodeResults; DataItem=null; target element is 'PrintBarcodesDocumentHelper' (HashCode=55335902); target property is 'Barcodes' (type 'IEnumerable`1')

Working resource class:

public class PrintBarcodesDocumentHelper : Freezable
{
    // Same properties

    protected override Freezable CreateInstanceCore()
    {
        return new PrintBarcodesDocumentHelper();
    }
}

Unfortunately i dont know why it have to be a Freezable.

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