c# - DataTemplateSelector.SelectTemplate 没有被调用`TreeView`的根项目

Question

我有一个TreeView：

<TreeView Grid.Row="0" Grid.Column="2" ItemsSource="{Binding ResourceInstanceRootItems}" SelectedItemChanged="TreeView_SelectedItemChanged_2">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Children}">
            <HierarchicalDataTemplate.ItemTemplateSelector>
                <local:ResourceInstDataTemplateSelector/>
            </HierarchicalDataTemplate.ItemTemplateSelector>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
 </TreeView>

和数据模板选择器：

public class ResourceInstDataTemplateSelector : DataTemplateSelector
{
    public override DataTemplate
        SelectTemplate(object item, DependencyObject container)
    {
        FrameworkElement element = container as FrameworkElement;

        if (element != null && item != null && item is ResourceInstance)
        {
            ResourceInstance ri = item as ResourceInstance;
            DataTemplate temp = null;
            if (ri.Parent == null)
                temp = App.Current.Resources["parent_item"] as DataTemplate;
            else if (ri.DependingInstance == null)
                temp = App.Current.Resources["simple_instance"] as DataTemplate;
            else
                temp = App.Current.Resources["dependent_instance"] as DataTemplate;

            return temp;
        }

        return null;
    }
}

问题是，ResourceInstDataTemplateSelector.SelectTemplate不会调用 中的根项目，TreeView它们仅显示为空箭头。

Answer 1

我相信您应该直接在 TreeView 上设置选择器，而不是在具有选择器的 TreeView 上放置 ItemTemplate，例如

<TreeView Grid.Row="0" Grid.Column="2" ItemsSource="{Binding ResourceInstanceRootItems}">
    <TreeView.ItemTemplateSelector>
        <local:ResourceInstDataTemplateSelector/>
    </TreeView.ItemTemplateSelector>
</TreeView>