c# - TreeViews 上的附加属性

Question

所以我有这个代码:

<Style TargetType="{x:Type TreeViewItem}">
    <Style.Resources>
        <Converters:GetElementTypeConverter x:Key="GetElementTypeConverter" />
    </Style.Resources>
    <Style.Triggers>
        <DataTrigger Binding="{Binding Path=., Converter={StaticResource GetElementTypeConverter}}" Value="{x:Type Models:ServerItem}">
            <Setter Property="CommandBehaviors:MouseDoubleClick.Command" Value="{Binding ConnectServer}" />
            <Setter Property="CommandBehaviors:MouseDoubleClick.CommandParameter" Value="{Binding Path=SelectedItem, RelativeSource={RelativeSource Self}}" />
            <Setter Property="Foreground" Value="Gray" />
        </DataTrigger>
        <DataTrigger Binding="{Binding Path=., Converter={StaticResource GetElementTypeConverter}}" Value="{x:Type Models:DatabaseItem}">
            <Setter Property="CommandBehaviors:MouseDoubleClick.Command" Value="{Binding ConnectDb}" />
            <Setter Property="CommandBehaviors:MouseDoubleClick.CommandParameter" Value="{Binding Path=SelectedItem, RelativeSource={RelativeSource Self}}" />
            <Setter Property="Foreground" Value="Red" />
        </DataTrigger>
    </Style.Triggers>
</Style>

它为 TreeView 项目定义了一些属性，但它并不完全有效 - 我的意思是它设置前景色，但是当我双击任何项目时，它不会触发我的命令。

Answer 1

我认为这与您之前的问题有关。

有了我昨天提到的这个设置，记住 RelayCommand<T>需要在相关元素而不是父虚拟机上。这就是为什么您可能会看到 Foreground属性工作正常，但命令从 DataContext 开始执行正在查找命令的位置(ServerItem 和 DatabaseItem)实际上并未定义命令 ConnectServer和 ConnectDb .

此外，设置 ConnectDb 而不是两个触发器默认并使用触发器设置ConnectServer只需 ServerItem的有关元素。

现在要解决您的问题，您可以定义 ConnectServer您的 ServerItem 中的命令和 ConnectDb您的 DatabaseItem 中的命令，或者如果您想将命令保留在 TreeView 的 DataContext 中, 使用 RelativeSource绑定(bind)以从 TreeView 中查找这些命令.

类似的东西(经过测试，效果很好):

<TreeView ItemsSource="{Binding ServerItems}">
  <TreeView.ItemContainerStyle>
    <Style TargetType="{x:Type TreeViewItem}">
      <Style.Resources>
        <CommandBehaviors:GetElementTypeConverter x:Key="GetElementTypeConverter" />
      </Style.Resources>
      <Setter Property="CommandBehaviors:MouseDoubleClick.Command"
              Value="{Binding Path=DataContext.ConnectDb,
                              RelativeSource={RelativeSource FindAncestor,
                                                              AncestorType={x:Type TreeView}}}" />
      <Setter Property="CommandBehaviors:MouseDoubleClick.CommandParameter"
              Value="{Binding Path=.}" />
      <Setter Property="Foreground"
              Value="Black" />
      <Style.Triggers>
        <DataTrigger Binding="{Binding Path=.,
                                        Converter={StaticResource GetElementTypeConverter}}"
                      Value="{x:Type CommandBehaviors:ServerItem}">
          <Setter Property="CommandBehaviors:MouseDoubleClick.Command"
                  Value="{Binding Path=DataContext.ConnectServer,
                                  RelativeSource={RelativeSource FindAncestor,
                                                                  AncestorType={x:Type TreeView}}}" />
          <Setter Property="Foreground"
                  Value="Tomato" />
        </DataTrigger>
      </Style.Triggers>
    </Style>
  </TreeView.ItemContainerStyle>
  <TreeView.ItemTemplate>
    <HierarchicalDataTemplate ItemsSource="{Binding Databases}">
      <TextBlock Text="{Binding}" />
    </HierarchicalDataTemplate>
  </TreeView.ItemTemplate>
</TreeView>

更新: (修复了 DoubleClick 的递归 TreeViewItem 事件调用)

在你的类(class) MouseDoubleClick
转变:

public class MouseDoubleClick {

  ...

  private static void OnMouseDoubleClick(object sender, RoutedEventArgs e) {
    Control control = sender as Control;
    ICommand command = (ICommand)control.GetValue(CommandProperty);
    object commandParameter = control.GetValue(CommandParameterProperty);
    command.Execute(commandParameter);
  }
}

到

public class MouseDoubleClick {

  ...

  private static void OnMouseDoubleClick(object sender, RoutedEventArgs e) {
    Control control = sender as Control;
    var possibleTreeViewItem = sender as TreeViewItem;
    if (control == null || (possibleTreeViewItem != null && !possibleTreeViewItem.IsSelected))
      return;
    ICommand command = (ICommand)control.GetValue(CommandProperty);
    object commandParameter = control.GetValue(CommandParameterProperty);
    command.Execute(commandParameter);
  }
}