绑定祖先不工作WPF

Question

我有一个TreeView,它被修改为在文本前面显示图像.所以我修改后的TreeViewItem被称为ImagedTreeViewItem.此ImagedTreeViewItem有一个Property,其中包含要显示的Image-Control图像.ImagedTreeViewItem还有一个属性,用于检查ImagedTreeViewItem-Icon是否为文件夹-Icon.此属性的名称为"IsFolder".

我的问题是: I'm Binding the Ancestors-Property (here: The ImagedTreeViewItem)获取我需要的数据.对于我的Image-Control,它完美地工作,对于我后来添加的上下文菜单没有.我不明白为什么,因为基本上它是同一个命令.

这是XAML中我的"ImagedTreeView"的代码:

<TreeView.Resources>
                <Style TargetType="{x:Type myClasses:ImagedTreeViewItem}">
                    <Setter Property="HeaderedItemsControl.HeaderTemplate">
                        <Setter.Value>
                            <DataTemplate>
                                <StackPanel Orientation="Horizontal">
<!-- Here it works!!! -->
                                    <Image Height="16" Source="{Binding Path=Icon, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type myClasses:ImagedTreeViewItem}}}" Stretch="Fill" Width="16" />
                                    <TextBlock Margin="5,0" Text="{Binding}" />
                                    <StackPanel.ContextMenu>
                                        <ContextMenu>
<!-- Here not :( -->
                                            <MenuItem Command="my:ImagedTreeView.AddFolder" Header="Add Folder"
                                                              IsEnabled="{Binding Path=IsFolder,
                                                              RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type myClasses:ImagedTreeViewItem}}}">
                                                <MenuItem.Icon>
                                                    <Image Source="folderadd16.png" />
                                                </MenuItem.Icon>
                                            </MenuItem>
                                            <!-- ... -->
                                        </ContextMenu>
                                    </StackPanel.ContextMenu>
                                </StackPanel>
                            </DataTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </TreeView.Resources>

我认为这段代码中的第二个绑定找不到祖先.Visual Studio的输出窗口告诉我同样的事情:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='....ImagedTreeViewItem', AncestorLevel='1''. BindingExpression:Path=IsFolder; DataItem=null; target element is 'MenuItem' (Name=''); target property is 'IsEnabled' (type 'Boolean')

Answer 1

ContextMenu不是VisualTree的一部分,这就是绑定失败的原因.您必须使用某种中继:ContextMenu.PlacementTarget和Tag属性作为第二次绑定搜索的缓存.我认为这会奏效:

<StackPanel Orientation="Horizontal"
            Tag="{Binding RelativeSource={RelativeSource AncestorType={x:Type myClasses:ImagedTreeViewItem}}}">
    <StackPanel.ContextMenu>
        <ContextMenu>
            <MenuItem Command="my:ImagedTreeView.AddFolder" Header="Add Folder"
                      IsEnabled="{Binding Path=PlacementTarget.Tag.IsFolder, RelativeSource={RelativeSource AncestorType=ContextMenu}}">
                <MenuItem.Icon>
                    <Image Source="folderadd16.png" />
                </MenuItem.Icon>
            </MenuItem>
            <!-- ... -->
        </ContextMenu>
    </StackPanel.ContextMenu>