TextBox样式不创建垂直滚动条

Question

I'm trying to create a style for my textbox, however when I add this template to the style the vertical scrollbars disappear.

<Style x:Key="MyTextBoxStyle" BasedOn="{x:Null}" TargetType="{x:Type TextBox}">
        <Setter Property="Foreground" Value="{DynamicResource BlueForegroundBrush}"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="BorderThickness" Value="0"/>
        <Setter Property="FontSize" Value="14"/>
        <Setter Property="Padding" Value="0,-5,0,0"/>
        <Setter Property="Width" Value="120"/>
        <Setter Property="Height" Value="100"/>
        <Setter Property="Focusable" Value="True"/>
        <Setter Property="AllowDrop" Value="True"/>
        <Setter Property="IsReadOnly" Value="True" />
        <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TextBox}">
                    <Grid>
                        <Rectangle x:Name="_rct" Stroke="#FFA8AFBE" RadiusX="8" RadiusY="8" Fill="White" />
                        <Border x:Name="_borderActive" BorderThickness="2" CornerRadius="8" BorderBrush="#FFA8AFBE" > 
                            <ListBox x:Name="Bd" SnapsToDevicePixels="true"
                                    Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}"
                                    BorderThickness="{TemplateBinding BorderThickness}"
                                    Margin="6">
                                <ScrollViewer x:Name="PART_ContentHost" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                            </ListBox>
                        </Border>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

Answer 1

I noticed that you are wrapping the ScrollViewer in a ListBox . The default template for a ListBox includes a ScrollViewer , so the interaction between them is most likely causing your ScrollBar issues.

What are you trying to accomplish by putting the ScrollViewer in a ListBox in your TextBox template? If we know why you are doing it, we can probably help you achieve the desired behavior.

The default template uses ListBoxChrome from the theme assembly to achieve the themed border look. If that is what you are after, this will work (note that you will need to add a reference to PresentationFramework.Aero):

<mwt:ListBoxChrome xmlns:mwt="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero"
                   Background="{TemplateBinding Background}" 
                   BorderBrush="{TemplateBinding BorderBrush}"
                   BorderThickness="{TemplateBinding BorderThickness}" 
                   RenderMouseOver="{TemplateBinding IsMouseOver}" 
                   RenderFocused="{TemplateBinding IsKeyboardFocusWithin}" 
                   SnapsToDevicePixels="True">
    <ScrollViewer Name="PART_ContentHost" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" /> 
</mwt:ListBoxChrome>