是否可以为“普通”集合定义TreeView分层视图模板？ [英] Is it possible to define a TreeView hierarchical view template for a 'plain' collection?

问题描述

我的模型类如下：

class Base 
{ 
    public string Name { get; set; }
}

class Item : Base { ... }

class Group : Base 
{
    public List<Base> GroupItems { get; private set; }
}

然后，我有一个的视图模型我填写的项目集合，如下面的 FillUp（）方法所示：

Then, I have a view model with an Items collection, that I fill up like shown in the FillUp() method below:

class ViewModel : INotifyPropertyChanged
{
    public ObservableCollection<Base> Items { get; set; }

    private void FillUp()
    {
        Item item1 = new Item { Name = "Item1" };
        Item item2 = new Item { Name = "Item2" };
        Group group = new Group { Name = "Group" };
        group.GroupItems.Add(item1);
        this.Items.Add(item1);
        this.Items.Add(item2);
        this.Items.Add(group);
    }
}

因此，我的项目集合现在包含2个类型为 Item 的对象和一个类型为 Group 的对象对 Item 对象之一的父母-孩子引用。

So, my Items collection now contains 2 objects of type Item and one object of type Group, which has a "parent-child" reference to one of the Item object.

我想要实现的目标：希望在 TreeView 中显示此模型，以便所有 Item 都属于某些尽管组应该显示为该组的子元素，尽管它们位于根集合中。

What I want to achieve: I'd like to display this model in a TreeView so that all the Items which belong to some Group should be displayed as child elements of that Group, despite of they are in the "root" collection.

它应该看起来像这样：

- Item2
+ Group
   - Item1

我可以使用 HierarchicalDataTemplate 来显示父子元素，但这不能让我从根集合中过滤掉属于某些组的那些项。

I could use a HierarchicalDataTemplate to display parent-child elements, but this does not let me filtering out those items from the root collection that belong to some groups.

<TreeView>
  <TreeView.Resources>
    <HierarchicalDataTemplate DataType = "{x:Type loc:Group}" ItemsSource = "{Binding GroupItems}">
      <TextBlock Text="{Binding Name}"/>
    </HierarchicalDataTemplate>

    <DataTemplate DataType="{x:Type loc:Item}">
      <TextBlock Text="{Binding Name}"/>
    </DataTemplate>
  </TreeView.Resources>
  <TreeViewItem ItemsSource="{Binding Items}"/>
</TreeView>

使用此视图，我得到了 Item1 两次：

With this view, I'm getting the "Item1" twice:

- Item1
- Item2
+ Group
    - Item1

是否有任何方法只能通过视图（XAML）标记获得所需的结果？否则，我应该更改视图模型，以便将 Item s仅添加到 Group s中，而不添加到

Is there any way to get the desired result via view (XAML) markup only? Otherwise, I should change my view model so that the Items will be only added into the Groups, not in the "root" collection (but that is what I try to avoid at the moment).

推荐答案

假设您有以下迹象：哪个项目属于一个组，在此示例中，我在组和项目类中添加了Guid。

Assuming you have some indication of which Item belongs in a group , for this example iv'e added a Guid in Group and Item classes.

您可以通过以下两种方式进行操作：

You can go about this in 2 ways :

1）创建一个复合包装器类。
并创建Wrapper类的ItemsSource。如果存在单个不属于某个组的项目，则子代将保持为空。

1) Create a composite wrapper class . And create an ItemsSource of Wrapper class . Where there is a single item which does not belong to a group , Children would just remain null.

public class Wrapper<T> where T : Base
{
    public List<T> Children { get; set; }
}

public class Base 
{ 
    public string Name { get; set; }
}

public class Item : Base
{
    public Guid GroupId { get; set; }
}

public class Group : Base 
{
    public Guid ID { get; set; }
    public List<Item> GroupItems { get; private set; }
}

第二个选择是使用CollectionView，并过滤出属于

your second option is to use a CollectionView , and filter out Items which belong to a group.

private ICollectionView _baseView;
public ICollectionView BaseView
{

    get
    {
        if (_baseView == null)
        {
            _baseView = new ListCollectionView((IList) items);
            _baseView.Filter = o => o is Group || o is Item && (o as Item).GroupId != Guid.Empty;                   
        }
        return _baseView;
    }
}

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