WPF基于数据类型的设置风格？ [英] WPF Setting style based on datatype?

问题描述

这是问题。我绑定一个TreeView与一些不同类型的对象。每个对象都是一个节点，SOME对象有一个名为IsNodeExpanded的属性，当然还有一些没有。这是我的风格：

Here's the problem. I'm binding a TreeView with a few different types of objects. Each object is a node, and SOME objects have a property called IsNodeExpanded, and of course, some others don't. Here's my style:

<Style TargetType="{x:Type TreeViewItem}">
    <Setter Property="IsExpanded" Value="{Binding IsNodeExpanded, Mode=TwoWay}" />
</Style>

现在，问题是绑定没有此属性的项目时，我们收到此错误在输出中：

Now, the problem is when binding the items that DON'T have this property, we get this error in the output:

System.Windows.Data Error: 39 : BindingExpression path error: 'IsNodeExpanded' property not found on 'object' ''CompensationChannel' (HashCode=56992474)'. BindingExpression:Path=IsNodeExpanded; DataItem='CompensationChannel' (HashCode=56992474); target element is 'TreeViewItem' (Name=''); target property is 'IsExpanded' (type 'Boolean')

当然我们得到它一吨。所以我试图提出一种方法来根据它所持有的DataType来切换TreeViewItem的样式。任何想法如何做到这一点？

Of course we get it a ton of times. So I'm trying to come up with a way to switch the style of the TreeViewItem based on the DataType it holds. Any idea on how to do this?

一些信息：我不能手动为每个项目，因为我不是在XAML中创建它们，它们是动态创建的来自数据源。

Some info: I can't do it manually for each item because I'm not creating them in XAML, they are created dynamically from a data source.

编辑：我发现这个答案，但它对我来说没有用。

I found this answer but it didn't work for me.

推荐答案

尝试使用 TreeView.ItemContainerStyleSelector 属性与自定义 StyleSelector 类更改样式取决于绑定对象是否具有该属性。

Try using the TreeView.ItemContainerStyleSelector property with a custom StyleSelector class which changes the style depending if the bound object has that property or not.

public class TreeItemStyleSelector : StyleSelector
{
    public Style HasExpandedItemStyle { get; set; }
    public Style NoExpandedItemStyle { get; set; }

    public override Style SelectStyle(object item, DependencyObject container)
    {
        // Choose your test
        bool hasExpandedProperty = item.GetType().GetProperty("IsExpanded") != null;

        return hasExpandedProperty
                   ? HasExpandedItemStyle
                   : NoExpandedItemStyle;
    }
}

在XAML资源中：

<Style x:Key="IsExpandedStyle" TargetType="{x:Type TreeViewItem}">
    <Setter Property="IsExpanded" Value="{Binding IsNodeExpanded, Mode=TwoWay}" />
</Style>

<Style x:Key="NoExpandedStyle" TargetType="{x:Type TreeViewItem}">
</Style>

<x:TreeViewItemStyleSelector x:Key="TreeViewItemStyleSelector"
                             HasExpandedItemStyle="{StaticResource IsExpandedStyle}"
                             NoExpandedItemStyle="{StaticResource NoExpandedStyle}" />

在XAML中：

<TreeView ItemsSource="{Binding ...}"
          ItemContainerStyleSelector="{StaticResource TreeItemStyleSelector}">

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