Question

I made some HeaderTemplate for Combobox.GroupStyle in order to display items in groups. And know I need to do some operations with the Combobox when user clicks on the GroupHeader. I have tried to write a trigger in my HedaerTemplate for Combobox.GroupStyle, but it doesn’t work. Below is full code of the combobox:

<ComboBox x:Name="comboBox" DisplayMemberPath="Type"
              HorizontalAlignment="Center" VerticalAlignment="Top"
              Margin="5" MinWidth="100">
        <ComboBox.GroupStyle>
            <GroupStyle>
                <GroupStyle.HeaderTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding Path=Name}"
                                   FontWeight="Bold"
                                   Margin="0,5,0,0"
                                   Padding="3" Background="LightGreen" MouseDown="TextBlock_MouseDown">
                        </TextBlock>
                        <DataTemplate.Triggers>
                            <EventTrigger RoutedEvent="TextBlock.MouseDown">
                                <EventTrigger.Actions>
                                    <BeginStoryboard>
                                        <Storyboard>
                                           <DoubleAnimation Storyboard.Target="{Binding  RelativeSource ={RelativeSource TemplatedParent}}"
                                                             From="0" Storyboard.TargetProperty="Width"
                                                                To="300" Duration="0:0:5"/>
                                        </Storyboard>
                                    </BeginStoryboard>
                                </EventTrigger.Actions>
                            </EventTrigger>
                        </DataTemplate.Triggers>
                    </DataTemplate>

                </GroupStyle.HeaderTemplate>
            </GroupStyle>
        </ComboBox.GroupStyle>
     </ComboBox>

I took the property “Width” just for example. But it didn’t work right. Animation expands GroupHeader, not entire ComboBox.

Answer 1

Your TemplateBinding binds to the item where the template is applied to, i.e., the header. Perhaps you need to set the binding as

{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=ComboBox}}

?

(Sorry, didn’t try the code myself.)