New Post: CheckComboBox - ItemTemplate

<ControlTemplate TargetType="{x:Type xctk:SelectorItem}">
                    <Border x:Name="_background" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
                        <CheckBox Content="{TemplateBinding Content}" />
                    </Border>
...

<ControlTemplate TargetType="{x:Type xctk:SelectorItem}">
                    <Border x:Name="_background" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
                        <CheckBox Content=kjhdslkjf" />
                    </Border>
...