綁定似乎在自定義DataTemplate（擴展程序）中不起作用

Question

總覽

我正在嘗試創建一個包含視覺樹的自定義擴展器，用戶可以在其中選擇或取消選擇節點。 但是這棵樹暫時並不重要。 重要的是必須覆蓋的標頭，這樣我才能顯示用戶需要的所有信息。

問題

不知何故，DataTemplate內部文本框的綁定根本無法工作。 無論我在字段中輸入什么，始終為空，並且不會調用DependencyProperty的setter。

碼

<UserControl x:Class="WPF_Test_project.CheckableTree"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             >
    <Grid>
        <Grid.Resources>
            <ResourceDictionary>
                <ControlTemplate x:Key="ExpanderToggleButton" TargetType="ToggleButton">
                    <Path Name="Chevron"
                          HorizontalAlignment="Center"
                          VerticalAlignment="Center"
                          Data="M 0 0 L 10 10 L 20 0 Z"
                          Fill="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Foreground}"
                          />

                    <!-- Change appearance when is expanded -->
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="true">
                            <Setter TargetName="Chevron" Property="Data" Value="M 0 10 L 10 0 L 20 10 Z" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>

                <Style x:Key="MainViewExpander" TargetType="Expander">
                    <Setter Property="Foreground" Value="Black" />
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="Expander">
                                <Grid>
                                    <Grid.RowDefinitions>
                                        <RowDefinition Height="Auto" />
                                        <RowDefinition Name="ContentRow" Height="0" />
                                    </Grid.RowDefinitions>
                                    <Border Name="HeaderBorder"
                                            Grid.Row="0"
                                            BorderThickness="0"
                                            Background="#FFE1E1E1"
                                            >
                                        <Grid>
                                            <Grid.ColumnDefinitions>
                                                <ColumnDefinition Width="*" />
                                                <ColumnDefinition Width="Auto" />
                                                <ColumnDefinition Width="20" />
                                            </Grid.ColumnDefinitions>

                                            <ContentPresenter
                                                Grid.Column="0"
                                                Margin="0"
                                                ContentSource="Header"
                                                RecognizesAccessKey="True" 
                                                />

                                            <ToggleButton
                                                Grid.Column="2"
                                                Margin="4 4 8 4"
                                                IsChecked="{Binding Path=IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
                                                OverridesDefaultStyle="True"
                                                Template="{StaticResource ExpanderToggleButton}"
                                                Background="Black"
                                                />

                                        </Grid>
                                    </Border>

                                    <Border Name="ContentBorder" Grid.Row="1" BorderThickness="0">
                                        <ContentPresenter Margin="0" />
                                    </Border>
                                </Grid>
                                <ControlTemplate.Triggers>
                                    <Trigger Property="IsExpanded" Value="True">
                                        <Setter TargetName="ContentRow" Property="Height" Value="{Binding ElementName=Content, Path=DesiredHeight}" />
                                    </Trigger>
                                </ControlTemplate.Triggers>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>

                    <Setter Property="HeaderTemplate">
                        <Setter.Value>
                            <DataTemplate>
                                <Grid>
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition Width="Auto" />
                                        <ColumnDefinition Width="*" />
                                        <ColumnDefinition Width="Auto" />
                                        <ColumnDefinition Width="Auto" />
                                        <ColumnDefinition Width="Auto" />
                                    </Grid.ColumnDefinitions>

                                    <CheckBox Grid.Column="0" 
                                              Margin="4" 
                                              />

                                    <TextBlock Grid.Column="1"
                                               Margin="2"
                                               Text="{Binding ElementName=CT, Path=Header, FallbackValue=Header}"
                                               Foreground="Black"
                                               FontWeight="Bold"
                                               FontSize="14" 
                                               />

                                    <TextBlock Grid.Column="2"
                                               Margin="2"
                                               Text="{Binding ElementName=CT, Path=NrOfFeaturesSelected, FallbackValue=5}" 
                                               Foreground="Black"
                                               FontWeight="Bold"
                                               FontSize="14" 
                                               HorizontalAlignment="Right"
                                               />

                                    <TextBlock Grid.Column="3"
                                               Margin="2"
                                               Text="/" 
                                               Foreground="Black"
                                               FontWeight="Bold"
                                               FontSize="14" 
                                               HorizontalAlignment="Right"
                                               />

                                    <TextBlock Grid.Column="4"
                                               Margin="2"
                                               Text="{Binding ElementName=CT, Path=NrOfFeaturesAvailable, FallbackValue=5}" 
                                               Foreground="Black"
                                               FontWeight="Bold"
                                               FontSize="14" 
                                               HorizontalAlignment="Right"
                                               />

                                </Grid>
                            </DataTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>

                <Style x:Key="TreeViewItemStyle" TargetType="TreeViewItem">
                    <Setter Property="IsExpanded" Value="{Binding IsExpanded}" />
                    <Setter Property="HorizontalContentAlignment" Value="Stretch" />
                </Style>

            </ResourceDictionary>
        </Grid.Resources>

        <Expander IsExpanded="True" Style="{StaticResource MainViewExpander}">
            <TreeView ItemsSource="{Binding ElementName=CT, Path=Items}"
                      BorderThickness="0"
                      ItemContainerStyle="{StaticResource TreeViewItemStyle}"
                      Padding="4"
                      >
                <TreeView.Resources>
                    <HierarchicalDataTemplate
                        x:Key="CheckableTreeItemTemplate"
                        ItemsSource="{Binding ElementName=CT, Path=Items}"
                        >

                        <Grid HorizontalAlignment="Stretch">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="Auto" />
                                <ColumnDefinition Width="Auto" />
                                <ColumnDefinition Width="*" />
                                <ColumnDefinition Width="Auto" />
                            </Grid.ColumnDefinitions>

                            <CheckBox Grid.Column="0"
                                      IsChecked="{Binding IsChecked}"
                                      VerticalAlignment="Center"
                                      Visibility="{Binding IsCheckable, Converter={StaticResource BooleanToVisibilityConverter}}"
                            />

                            <Label Grid.Column="1" 
                                   Content="{Binding Title}" 
                                   HorizontalAlignment="Left" 
                                   VerticalAlignment="Center"
                            />

                            <Label Grid.Column="3" 
                                   Content="{Binding TagCountDisplayValue}" 
                                   HorizontalAlignment="Right" 
                                   VerticalAlignment="Center" 
                                   Visibility="{Binding ShowTagCountDisplayValue, Converter={StaticResource BooleanToVisibilityConverter}}"
                            />

                        </Grid>
                    </HierarchicalDataTemplate>
                </TreeView.Resources>
            </TreeView>
        </Expander>
    </Grid>
</UserControl>

類

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;

namespace WPF_Test_project
{
    /// <summary>
    /// Interaction logic for CheckableTree.xaml
    /// </summary>
    public partial class CheckableTree : UserControl
    {
        public CheckableTree()
        {
            InitializeComponent();
        }

        public int NrOfFeaturesSelected
        {
            get { return (int)GetValue(NrOfFeaturesSelectedProperty); }
            set { SetValue(NrOfFeaturesSelectedProperty, value); }
        }

        public static readonly DependencyProperty NrOfFeaturesSelectedProperty =
            DependencyProperty.Register("NrOfFeaturesSelected", typeof(Int32), typeof(CheckableTree), new UIPropertyMetadata(null));


        public int NrOfFeaturesAvailable
        {
            get { return (int)GetValue(NrOfFeaturesSelectedProperty); }
            set { SetValue(NrOfFeaturesSelectedProperty, value); }
        }

        public static readonly DependencyProperty NrOfFeaturesAvailableProperty =
            DependencyProperty.Register("NrOfFeaturesAvailable", typeof(Int32), typeof(CheckableTree), new UIPropertyMetadata(null));


        public IEnumerable<object> Items
        {
            get { return (IEnumerable<object>)GetValue(ItemsProperty); }
            set { SetValue(NrOfFeaturesSelectedProperty, value); }
        }

        public static readonly DependencyProperty ItemsProperty =
            DependencyProperty.Register("Items", typeof(IEnumerable<object>), typeof(CheckableTree), new UIPropertyMetadata(null));


        public string Header
        {
            get { return (string)GetValue(HeaderProperty); }
            set { SetValue(HeaderProperty, value); }
        }

        public static readonly DependencyProperty HeaderProperty =
            DependencyProperty.Register("Header", typeof(string), typeof(CheckableTree), new UIPropertyMetadata(null));

    }
}

用法

        <local:CheckableTree Header="Test" NrOfFeaturesSelected="9">

        </local:CheckableTree>

但是我總是得到“后備值”。 有人知道為什么會這樣嗎？ 我是否必須將DataTemplate鏈接到控件類？

解決方案 （感謝mm8）

對於DataTemplate中的每個綁定，請參考父級UserControl

<Textbox
...
Text={Binding Path=XY, RelativeSource={RelativeSource AncestorType=UserControl}, FallbackValue=...}"
... />

Answer 1

嘗試使用{RelativeSource}綁定到父UserControl的Header屬性：

<TextBlock Grid.Column="1"
            Margin="2"
            Text="{Binding Path=Header, RelativeSource={RelativeSource AncestorType=UserControl}, FallbackValue=Header}"
            Foreground="Black"
            FontWeight="Bold"
            FontSize="14" 
            />