c# - 将命令附加到 TreeView 子项 - 与嵌套子项不同

Question

我正在使用这里的代码:WPF/MVVM - how to handle double-click on TreeViewItems in the ViewModel? ，来自已接受的答案。我的xaml是这样的:

<TreeView CommandBehaviors:MouseDoubleClick.Command="{Binding ConnectServer}" CommandBehaviors:MouseDoubleClick.CommandParameter="{Binding Path=SelectedItem, RelativeSource={RelativeSource Self}}" 
                                  Grid.Column="0" HorizontalAlignment="Stretch" DockPanel.Dock="Left" ItemsSource="{Binding Path=ServerItems, UpdateSourceTrigger=PropertyChanged}">
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <Setter Property="CommandBehaviors:MouseDoubleClick.Command" Value="{Binding ConnectDb}"/>
            <Setter Property="CommandBehaviors:MouseDoubleClick.CommandParameter" Value="{Binding Path=SelectedItem, RelativeSource={RelativeSource Self}}"/>
        </Style>
    </TreeView.ItemContainerStyle>
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Databases}">
            <TextBlock Text="{Binding}" />
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

来自 Style 标记的附加命令不起作用，而且也不应该起作用，因为 TreeView 标记级别上已经附加了一个命令。我想做的是为顶级 child 执行一个命令，为较低级别的 child 执行另一个命令。我该怎么做？

编辑:

那么，正如 Viv 建议的那样 - 如何检查 Treeviewitem 是否是根节点？

Answer 1

类似于:

<Window.Resources>
  <CommandBehaviors:IsRootNodeConverter x:Key="IsRootNodeConverter" />
</Window.Resources>
<Grid>
  <TreeView>
    <TreeView.ItemContainerStyle>
      <Style TargetType="{x:Type TreeViewItem}">
        <Setter Property="CommandBehaviors:MouseDoubleClick.Command"
                Value="{Binding ConnectDb}" />
        <Setter Property="CommandBehaviors:MouseDoubleClick.CommandParameter"
                Value="{Binding Path=SelectedItem,
                                RelativeSource={RelativeSource Self}}" />
        <Setter Property="Foreground"
                Value="Black" />
        <Style.Triggers>
          <DataTrigger Binding="{Binding Path=.,
                                          RelativeSource={RelativeSource Self},
                                          Converter={StaticResource IsRootNodeConverter}}"
                        Value="True">
            <Setter Property="CommandBehaviors:MouseDoubleClick.Command"
                    Value="{Binding ConnectServer}" />
            <Setter Property="Foreground"
                    Value="Tomato" />
          </DataTrigger>
        </Style.Triggers>
      </Style>
    </TreeView.ItemContainerStyle>
    <TreeView.ItemTemplate>
      <HierarchicalDataTemplate>
        <!--<TreeViewItem>-->
          <TextBlock Text="{Binding}" />
        <!--</TreeViewItem>-->
      </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
    <TreeViewItem Header="1">
      <TreeViewItem Header="A" />
      <TreeViewItem Header="B">
        <TreeViewItem Header="AA" />
        <TreeViewItem Header="AB" />
        <TreeViewItem Header="AC" />
      </TreeViewItem>
      <TreeViewItem Header="C" />
    </TreeViewItem>
  </TreeView>
</Grid>

和转换器:

class IsRootNodeConverter : IValueConverter
{
  public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
    TreeViewItem item = value as TreeViewItem;
    if (item == null || item.Parent == null)
      return false;
    return !Object.ReferenceEquals(value.GetType(), item.Parent.GetType());
  }

  public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) {
    throw new NotImplementedException();
  }
}

我故意从 Style Trigger 中省略了 CommandBehaviors:MouseDoubleClick.CommandParameter，因为它似乎没有从默认值更改。刚刚添加了一个 Foreground 属性用于测试，您也可以将其删除。