Silverlight AutoCompleteBox BorderBrush runtime color change? - silverlight

Question

Is it possible to update a templated AutoCompleteBox's BorderBrush at runtime? I can't seem to set the BorderBrush or the background.
Even base statements like TxtFoodSearch.BorderBrush = new SolidColorBrush(Colors.Red) don't seem to made a difference after the page has loaded.
My Xaml is below.
<controls:AutoCompleteBox x:Name="MyAutoCompleteSample" Margin="17,24,58,32" FontSize="12">
<controls:AutoCompleteBox.Style>
<Style TargetType="controls:AutoCompleteBox">
<Setter Property="IsTabStop" Value="False" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="controls:AutoCompleteBox">
<Grid Margin="{TemplateBinding Padding}"
Background="{TemplateBinding Background}">
<TextBox IsTabStop="True" x:Name="Text" Style="{TemplateBinding TextBoxStyle}" Margin="0"
KeyDown="MyAutoCompleteSample_KeyDown"
/>
<Popup x:Name="Popup">
<Border x:Name="PopupBorder" HorizontalAlignment="Stretch" Opacity="0.0" BorderThickness="0" CornerRadius="3">
<Border.RenderTransform>
<TranslateTransform X="1" Y="1" />
</Border.RenderTransform>
<Border.Background>
<SolidColorBrush Color="#11000000" />
</Border.Background>
<Border
HorizontalAlignment="Stretch"
Opacity="1.0"
Padding="0"
ToolTipService.ToolTip="Select or enter your food selection"
BorderThickness="{TemplateBinding BorderThickness}"
BorderBrush="{TemplateBinding BorderBrush}"
CornerRadius="3">
<Border.RenderTransform>
<TransformGroup>
<TranslateTransform X="-1" Y="-1" />
</TransformGroup>
</Border.RenderTransform>
<Border.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FFDDDDDD" Offset="0"/>
<GradientStop Color="#AADDDDDD" Offset="1"/>
</LinearGradientBrush>
</Border.Background>
<ListBox
x:Name="SelectionAdapter"
ScrollViewer.HorizontalScrollBarVisibility="Auto"
ScrollViewer.VerticalScrollBarVisibility="Auto"
ItemContainerStyle="{TemplateBinding ItemContainerStyle}"
ItemTemplate="{TemplateBinding ItemTemplate}" />
</Border>
</Border>
</Popup>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="PopupStates">
<VisualStateGroup.Transitions>
<VisualTransition GeneratedDuration="0:0:0.1" To="PopupOpened" />
<VisualTransition GeneratedDuration="0:0:0.2" To="PopupClosed" />
</VisualStateGroup.Transitions>
<VisualState x:Name="PopupOpened">
<Storyboard>
<DoubleAnimation Storyboard.TargetName="PopupBorder" Storyboard.TargetProperty="Opacity" To="1.0" />
</Storyboard>
</VisualState>
<VisualState x:Name="PopupClosed">
<Storyboard>
<DoubleAnimation Storyboard.TargetName="PopupBorder" Storyboard.TargetProperty="Opacity" To="0.0" />
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</controls:AutoCompleteBox.Style>
</controls:AutoCompleteBox>

Answer 1

One way I've managed to find how to address the styling through code is the following.
Walk the visual tree and get the AutoCompleteBox, cast that into a textbox, then adjust the colors (border, background, etc)
//Cast into textbox
TextBox Temp = VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(MyAutoCompleteControl, 0), 0) as TextBox;
Temp.BorderBrush = new SolidColorBrush(Colors.Red);//Change border color
I'm sure there is a better way, but this seems to work.

Answer 2

If you're using Silverlight 3 (where styles can be set multiple times), then it is easier: you can actually set the TextBoxStyle (on MSDN here).
You can then create a new Style in code-behind (a pain), or perhaps change/apply another of your pre-defined styles in code.