自定义未在RadComboBox中显示的模板更改。为什么？

Question

我有RadComboBox。像：

 <telerik:RadComboBox Grid.Row="4" Grid.Column="1" Name="truckComboBox" Width="280" Height="30"  Margin="5,35,5,5"  StaysOpenOnEdit="True"  
                                             IsSynchronizedWithCurrentItem="True" Template="{StaticResource RadComboBoxControlTemplate1}"
                             DisplayMemberPath="Description" EmptyText="Select" OpenDropDownOnFocus="True" HorizontalAlignment="Left"
                             ItemsSource="{Binding  TrucksCV, UpdateSourceTrigger=PropertyChanged}" TextSearchMode="Contains" IsFilteringEnabled="True" IsEditable="True" SelectedValue="{Binding TechUserModel.TruckID, Mode=TwoWay}">
                                            <telerik:RadComboBox.ItemContainerStyle>
                                                <Style TargetType="{x:Type telerik:RadComboBoxItem}">
                                                    <Setter Property="FontSize" Value="18"></Setter>
                                                    <Setter Property="FontWeight" Value="SemiBold"></Setter>
                                                </Style> 
                                            </telerik:RadComboBox.ItemContainerStyle>

                                        </telerik:RadComboBox>

我想增加箭头按钮的高度，我们自定义模板，如：

   <ControlTemplate x:Key="RadComboBoxControlTemplate1" TargetType="{x:Type telerik:RadComboBox}">
                    <Grid x:Name="VisualRoot">
                        <Border Background="{TemplateBinding Background}" CornerRadius="1" IsHitTestVisible="False"/>
                        <telerik:RadToggleButton x:Name="PART_DropDownButton" ClickMode="Press" IsTabStop="False" Margin="0" Padding="0" Width="100">
                            <telerik:RadToggleButton.Template>
                                <ControlTemplate TargetType="{x:Type telerik:RadToggleButton}">
                                    <ContentPresenter ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" ContentStringFormat="{TemplateBinding ContentStringFormat}" Width="100"/>
                                </ControlTemplate>
                            </telerik:RadToggleButton.Template>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="*"/>
                                    <ColumnDefinition Width="Auto"/>
                                </Grid.ColumnDefinitions>
                                <Telerik_Windows_Controls_Chromes:ButtonChrome x:Name="ButtonChrome" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Grid.ColumnSpan="2" CornerRadius="1" RenderMouseOver="{TemplateBinding IsMouseOver}" RenderPressed="{TemplateBinding IsDropDownOpen}" RenderFocused="{TemplateBinding IsFocused}" RenderEnabled="{TemplateBinding IsEnabled}" Width="100">
                                    <telerik:StyleManager.Theme>
                                        <telerik:Office_BlackTheme/>
                                    </telerik:StyleManager.Theme>
                                </Telerik_Windows_Controls_Chromes:ButtonChrome>
                                <ContentControl x:Name="DropDownIcon" Background="White" Grid.Column="1" Foreground="Black" IsTabStop="False">
                                    <ContentControl.Template>
                                        <ControlTemplate TargetType="{x:Type ContentControl}">
                                            <Grid Margin="5,0">
                                                <Path x:Name="BackgroundIcon" Data="M0,0L2,0 1,1z" Fill="{TemplateBinding Background}" Height="3" Margin="0,2,0,0" Stretch="Fill" Width="5"/>
                                                <Path x:Name="ForegroundIcon" Data="M0,0L2,0 1,1z" Fill="{TemplateBinding Foreground}" Height="3" Margin="0,1" Stretch="Fill" Width="5"/>
                                            </Grid>
                                        </ControlTemplate>
                                    </ContentControl.Template>
                                </ContentControl>
                                <ContentPresenter x:Name="Content" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" Content="{TemplateBinding SelectionBoxItem}" Grid.Column="0" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" IsHitTestVisible="False" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                            </Grid>
                        </telerik:RadToggleButton>

                    </Grid>

                </ControlTemplate>

但是当我们运行应用程序时，RadComboBox没有显示任何更改原因？请提供我的问题的完整解决方案。提前谢谢。