Change TextBox Template without losing classic behavior

Question

I've create a custom control which inherit from WPF TextBox.

My Control Template simply add a small button on textbox in order to delete its text quicker.

However, I've noticed that when my textBox got the focus, its border doesn't change (blue color) as is the case for classic textbox.

I would preserver all aspect of original textBox, just like the border when the control get focus.

Am I missing something?

@@EDIT

<TextBox x:Class="XTextBox.WKTextBox"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         Height="23" Width="200"
         >



<TextBox.Resources>
    <ControlTemplate x:Key="IconButton" TargetType="{x:Type ToggleButton}">
        <Border>
            <ContentPresenter />
        </Border>
    </ControlTemplate>
</TextBox.Resources>

<TextBox.Style>

    <Style TargetType="TextBox">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type TextBox}">
                    <Grid>
                        <Border BorderThickness="1" BorderBrush="DarkGray">
                            <ScrollViewer x:Name="PART_ContentHost" />
                        </Border>
                        <ToggleButton Template="{StaticResource IconButton}"
                          MaxHeight="21" 
                          Margin="-1,0,0,0" 
                          Name="imgButton" 
                          Focusable="False"
                          IsChecked="False">

                            <Image Name="imgClearText" Source="Images\x.png" Stretch="Uniform" Opacity="0.5" Visibility="Visible" HorizontalAlignment="Right"  >
                            </Image>

                        </ToggleButton>

                    </Grid>

                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</TextBox.Style>

Answer 1

Unfortunately, you can't simply Replace part of default template in WPF without loosing functionallity. I believe the easiest solution would be to donwload Blend (it comes with VS2015). Open it, create an emty textbox and edit its template:

Blend will make a copy of default template, so you won't loose any of your default behaviour, like selection, focus etc. Then you can save a project, open it in VS and refactor it as you want. Like moving style to dictionary or something.

Answer 2

You can manually get the same effect by adding handlers for the GotFocus & LostFocus events of the Border and set the highlight colors you want there.

<Border BorderThickness="1" BorderBrush="DarkGray" LostFocus="Border_LostFocus" GotFocus="Border_GotFocus">

and in your .cs file

private void Border_LostFocus(object sender, RoutedEventArgs e)
{
  ((Border)sender).BorderBrush = new SolidColorBrush(Colors.DarkGray);
}

private void Border_GotFocus(object sender, RoutedEventArgs e)
{
  ((Border)sender).BorderBrush = new SolidColorBrush(Colors.LightBlue);
}