ComboBox stops reacting when a DynamicResource template is assigned to it

Question

I have a simple combobox that works fine except when i assign a template to it.
The original combobox code is:

<Window x:Class="TemplatesStylesAndThemes.ComboBoxesResources"  
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"  
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"  
        xmlns:local="clr-namespace:TemplatesStylesAndThemes"  
        mc:Ignorable="d"  
        Title="ComboBoxesResources" Height="450" Width="800">  
    <Grid>  
        <ComboBox x:Name="comboBoxMaritalStatus" Grid.Column="0" HorizontalAlignment="Left" Margin="12,6,0,0" Grid.Row="0"   
                  VerticalAlignment="Top" Width="105" Height="25">  
  
        </ComboBox>  
    </Grid>  
</Window>  
  

this works fine. If I add a template to it, the functionality of the combobox disappears ... That is when the ComboBox becomes:

<ComboBox x:Name="comboBoxMaritalStatus" Template="{DynamicResource XYComboBoxTemplate}" HorizontalAlignment="Left" Margin="12,6,0,0"    
                  VerticalAlignment="Top" Width="105" Height="25">  

the combobox does not react to mouse events at all - it just displays a rectangle with no "life"

The template is an Application.Resource and is defined in App.xaml as:

<Application x:Class="TemplatesStylesAndThemes.App"  
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
             xmlns:local="clr-namespace:TemplatesStylesAndThemes"  
             StartupUri="ComboBoxesResources.xaml">  
    <Application.Resources>  
        <ControlTemplate x:Key="XYComboBoxTemplate" TargetType="ComboBox" >  
            <Border Name="RootElement" >  
                <Border.Background>  
                    <SolidColorBrush x:Name="BorderBrush" Color="LightCyan"/>  
                </Border.Background>  
  
            </Border>  
            <ControlTemplate.Triggers>  
                <Trigger Property="IsDropDownOpen" Value="True" >  
                    <Setter Property="Background" Value="Red"/>  
                </Trigger>  
            </ControlTemplate.Triggers>  
        </ControlTemplate>  
    </Application.Resources>  
</Application>  
  

What am I doing wrong?

Answer 1

Hi,@Juan Dent . Welcome Microsoft Q&A.

To modify the background color of the ComboBox as needed, it is necessary to modify the ControlTemplate of the ComboBox .
You could refer to the following code to modify and use the default template of Combobox.

Get the default template of Combobox in xaml.

Style:
Find and modify the value of ComboBox.Static.Background in the newly created resource.

    <SolidColorBrush x:Key="ComboBox.Static.Background" Color="LightCyan"/>  

Add the following code in the ControlTemplate.Triggers of the ComboBoxToggleButton style.

 <MultiDataTrigger>  
                                <MultiDataTrigger.Conditions>  
                                    <Condition Binding="{Binding IsDropDownOpen, RelativeSource={RelativeSource AncestorType={x:Type ComboBox}}}" Value="true"/>  
                                </MultiDataTrigger.Conditions>  
                                <Setter Property="Background" TargetName="templateRoot" Value="red"/>  
                                <Setter Property="BorderBrush" TargetName="templateRoot" Value="{StaticResource ComboBox.MouseOver.Editable.Border}"/>  
                                <Setter Property="Background" TargetName="splitBorder" Value="red"/>  
                                <Setter Property="BorderBrush" TargetName="splitBorder" Value="{StaticResource ComboBox.MouseOver.Editable.Button.Border}"/>  
                            </MultiDataTrigger>  

The complete code:
229015-5.txt

The result:

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