无法将ObservableCollection绑定到列出来自xaml的dp [英] Cannot bind ObservableCollection to List dp from xaml

问题描述

我有一个名为Switch的userControl，它具有List的DependancyProperty类型，名为ImageList。
在我的ViewModel中，我创建一个名为imgList的ObservableCollection。
在我的XAML窗口中，我写下列行：

 < loc：switch ImageList = {Binding imgList} /> 
  

为了我最大的遗憾，这根本不起作用，ImageList没有收到请求的值。 / p>

ImageList定义如下：

  public static readonly DependancyProperty ImageListProperty = DependancyProperty.Register 
（ImageList，typeof（List< ImageSource>），typeof（Switch））; 
 
 public List< ImageSource> ImageList {
 get {return（List< ImageSource>）GetValue（ImageListProperty）; } 
 set {SetValue（ImageListProperty，value）; } 
} 
  

viewModel是正确的，如下所示：

 < ComboBox ItemsSource = {Binding imgList} /> 
  

有趣的是，这可以正常工作：

 < loc：switch> 
< loc：switch.ImageList> 
< BitmapImage UriSource =Bla.png/> 
< BitmapImage UriSource =Bla2.png/> 
< / loc：switch.ImageList> 
< / loc：switch> 
  

提前感谢

解决方案

如何预期 ObservableCollection type（imgList）的传入值将与 List<> type（Switch.ImageList）？

请使您的类型兼容。

一种方法是将 ImageListProperty 重新声明为 IList 类型为 ObservableCollection<> / code>实现 IList 界面。

在WPF中，绑定将会在目标属性的类型相同时出现或基本类型到源值。 ObservableCollection 不从列表<> 中导出。

编辑

您的最后一个示例停止工作，因为 IList 不会隐式实例化作为接口），而没有通过XAML提供给它的显式集合类型。将 ImageListProperty 更改为 IList （不是 IList< T> ）

你应该以这种方式改变....

  < loc：switch xmlns：coll =clr-namespace：System.Collections; assembly = mscorlib> 
< loc：switch.ImageList> 
< coll：ArrayList> 
< BitmapImage UriSource =Bla.png/> 
< BitmapImage UriSource =Bla2.png/> 
< / coll：ArrayList> 
< / loc：switch.ImageList> 
< / loc：switch> 
  

这是因为 ArrayList 是一个具体的XAML实现 IList 的序列化集合。而 ObservableCollection<> 也是简单的 IList 。

I have a userControl named Switch which has a DependancyProperty of type List, named ImageList. In my ViewModel, I create a ObservableCollection named imgList. In My XAML window, I write the following line:

<loc:switch ImageList={Binding imgList}/>

To my greatest regret, this does not work at all and ImageList does not recieve the requested values.

ImageList is defined as the following:

public static readonly DependancyProperty ImageListProperty = DependancyProperty.Register
  ("ImageList", typeof(List<ImageSource>), typeof(Switch));

public List<ImageSource> ImageList {
  get { return (List<ImageSource>)GetValue(ImageListProperty); }
  set { SetValue(ImageListProperty, value); }
}

The viewModel is correct, as the following works:

<ComboBox ItemsSource={Binding imgList}/>

It is interesting to note that this works correctly:

<loc:switch>
  <loc:switch.ImageList>
    <BitmapImage UriSource="Bla.png"/>
    <BitmapImage UriSource="Bla2.png"/>
  </loc:switch.ImageList>
</loc:switch>

Thanks in advance!

解决方案

How do you expect an incoming value of ObservableCollection<> type (imgList) would match with List<> type (Switch.ImageList)?

Please make your types compatible.

One way is to redeclare ImageListProperty to IList<> type as ObservableCollection<> implements IList interface.

In WPF Binding would wouk when the target property's type is same or a base type to the source value. ObservableCollection doesnt derive from List<>.

EDIT

Your last example stops working because IList<> isnt instantiated implicitly (being an Interface) without explicit collection type supplied to it via XAML. Change ImageListProperty to IList (Not IList<T>).

You should it change this way....

 <loc:switch xmlns:coll="clr-namespace:System.Collections;assembly=mscorlib">
   <loc:switch.ImageList>
     <coll:ArrayList>
         <BitmapImage UriSource="Bla.png"/>
         <BitmapImage UriSource="Bla2.png"/>
     </coll:ArrayList>
   </loc:switch.ImageList>
 </loc:switch>

This works because ArrayList is a concrete XAML serialized collection that implements IList. And ObservableCollection<> also does plain IList.

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