wpf 中自定义样式的文本框文本始终为空

Question

Hey I'm designing a new style for a textbox in my WPF application using XAML codes. The textbox is a combination of textbox and textblock, I used the textblock to show name of the textbox when the text is null, and disappears when the text is filled, but there is a problem when I run the app and fill something in the textbox it seems that it's working properly but in the backend when I want to access the textbox Text it's null even though it's filled!!!! Am I doing something wrong from the base or I missed something to do.

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Style TargetType="{x:Type TextBox}"
           x:Key="TextBoxTheme">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TextBox}">
                    <Border CornerRadius="10"
                            Background="#353340"
                            Width="200"
                            Height="40">
                        <Grid>
                            <Rectangle StrokeThickness="1"/>
                            <TextBox Margin="1" 
                                     Text="{TemplateBinding Property=Text}"
                                     BorderThickness="0"
                                     Background="Transparent"
                                     VerticalAlignment="Center"
                                     Padding="5"
                                     Foreground="#CFCFCF"
                                     x:Name="textBox"/>
                            <TextBlock IsHitTestVisible="False"
                                       Text="{TemplateBinding Name}"
                                       VerticalAlignment="Center"
                                       HorizontalAlignment="Left"
                                       Margin="10, 0, 0, 0"
                                       FontSize="11"
                                       Foreground="DarkGray">
                                <TextBlock.Style>
                                    <Style TargetType="{x:Type TextBlock}">
                                        <Style.Triggers>
                                            <DataTrigger Binding="{Binding Text, ElementName=textBox}" Value="">
                                                <Setter Property="Visibility" Value="Visible"/>
                                            </DataTrigger>
                                        </Style.Triggers>
                                        <Setter Property="Visibility" Value="Hidden"/>
                                    </Style>
                                </TextBlock.Style>
                            </TextBlock>
                        </Grid>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>

    </Style>
</ResourceDictionary>

Answer 1

Instead of giving the TextBox an area to display its contents, you have overlapped it on top with another TextBox.
To display its content, the TextBox looks in the Template for ScrollViewer x:Name="PART_ContentHost" .

Try a Template like this:

            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type TextBox}">
                        <Border x:Name="border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
                            <Grid>
                                <TextBlock x:Name="PART_TextBlock" Text="{TemplateBinding Name}" Visibility="Collapsed"/>
                                <ScrollViewer x:Name="PART_ContentHost"
                                          Focusable="false"
                                          HorizontalScrollBarVisibility="Hidden"
                                          VerticalScrollBarVisibility="Hidden"/>
                            </Grid>
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="Text"
                                         Value="{x:Static sys:String.Empty}">
                                <Setter TargetName="PART_TextBlock" Property="Visibility" Value="Visible"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>

Answer 2

If you check the documentation for TemplateBinding you'll see it's just syntactic sugar for a one-way RelativeSource binding to the templated parent, so all you need to do is change your TextBox binding to make it two-way:

Text="{Binding Path=Text, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"

Also, I disagree with the comment above about this not being a good idea, one of the whole purposes of WPF's templating system is to make it possible to template existing controls eg for redistribution of libraries etc. That said, I don't think Name is the best property to use for your hint text, if for no other reason than the fact that it doesn't allow spaces. A much better solution would be to use an attached property . For a quick-and-dirty solution there's also the Tag property, which you're free to use for whatever you want.