DataBinding - 值通过 DataTemplate 不可见

Question

我的 xaml 中有以下 DataTemplate：

<DataGrid x:Name="ChecklistDataGrid" AutoGenerateColumns="False" HorizontalAlignment="Stretch" Foreground="White" VerticalAlignment="Stretch" Background="Transparent" 
          RowBackground="Transparent" AlternatingRowBackground="Transparent" HorizontalGridLinesBrush="White" VerticalGridLinesBrush="White" CanUserAddRows="False" SelectionUnit="Cell">
    <DataGrid.Resources>
        <!-- Custom Style for DataGridColumnHeader -->
        <Style TargetType="DataGridColumnHeader">
            <Setter Property="Background" Value="Transparent"/>
            <Setter Property="BorderBrush" Value="Transparent"/>
            <Setter Property="Foreground" Value="White"/>
        </Style>


        <!-- DataTemplate for Buttons -->
        <DataTemplate x:Key="ButtonTemplate">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Button Content="IO" Background="Green" Click="IOButton_Click" HorizontalAlignment="Stretch" Grid.Column="0"/>
                <Button Content="NIO" Background="Red" Click="NIOButton_Click"  HorizontalAlignment="Stretch" Grid.Column="1"/>
                <Button Content="NR" Background="DarkGray" Click="NRButton_Click"  HorizontalAlignment="Stretch" Grid.Column="2"/>
            </Grid>
        </DataTemplate>

        <!-- DataTemplate for TextBox with NR Button -->
        <DataTemplate x:Key="TextBoxTemplate">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <TextBox Text="{Binding Pruefwert, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Background="White"   HorizontalAlignment="Stretch" Grid.Column="0" Grid.ColumnSpan="2" TextChanged="TextBox_TextChanged"/>
                <Button Content="NR" Background="DarkGray" Click="NRButton_Click"  HorizontalAlignment="Stretch" Grid.Column="2"/>
            </Grid>
        </DataTemplate>

    </DataGrid.Resources>

    <DataGrid.Columns>
        <DataGridTextColumn Header="Pruefpunkt" Binding="{Binding Pruefpunkt}" Width="1*"/>

        <!-- Wrapping Text Column -->
        <DataGridTemplateColumn Header="Content" Width="10*">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Content}" TextWrapping="Wrap" Background="{Binding ContentBackground}"/>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>

        <!-- Conditional Column for Buttons or TextBox -->
        <DataGridTemplateColumn Header="Actions" Width="3*">
            <DataGridTemplateColumn.CellTemplate>
                <DataTemplate>
                    <ContentControl>
                        <ContentControl.Style>
                            <Style TargetType="ContentControl">
                                <Style.Triggers>
                                    <DataTrigger Binding="{Binding Type}" Value="button">
                                        <Setter Property="ContentTemplate" Value="{StaticResource ButtonTemplate}" />
                                    </DataTrigger>
                                    <DataTrigger Binding="{Binding Type}" Value="text">
                                        <Setter Property="ContentTemplate" Value="{StaticResource TextBoxTemplate}" />
                                    </DataTrigger>
                                </Style.Triggers>
                            </Style>
                    </ContentControl.Style>
                    </ContentControl>
                </DataTemplate>
            </DataGridTemplateColumn.CellTemplate>
        </DataGridTemplateColumn>
        <DataGridTextColumn Header="Pruefpunkt" Binding="{Binding Pruefwert}" Width="1*"/>
    </DataGrid.Columns>
</DataGrid>

我遇到的问题是，Pruefwert 的值在文本框中不可见。对于数据模板文本框模板

我在末尾添加了一个额外的 DataGridTextColumn，具有相同的 DataBinding，这里的值是可见的，没有任何问题。所以数据模板肯定存在一些绑定问题。而且我没有收到任何绑定错误。

Answer 1

为了应用 DataTemplate，首先必须有某个要应用它的对象。对于 ContentTemplate，此对象将是 Content 属性的值。但你这个属性里什么都没有，它被设置为null。

参见示例：

    <StackPanel>
        <FrameworkElement.Resources>
            <DataTemplate x:Key="point.template" DataType="Point">
                <StackPanel Orientation="Horizontal">
                    <TextBlock Text="{Binding X}" Margin="5"/>
                    <TextBlock Text="{Binding Y}" Margin="5"/>
                </StackPanel>
            </DataTemplate>
        </FrameworkElement.Resources>
        <FrameworkElement.DataContext>
            <Point X="123" Y="456"/>
        </FrameworkElement.DataContext>
        <ContentControl ContentTemplate="{DynamicResource point.template}"/>
        <ContentControl ContentTemplate="{DynamicResource point.template}"
                        Content="{Binding}"/>
    </StackPanel>