<Style.Triggers>
  <Trigger Property="IsEnabled" Value="false">
    <Setter Property="Background" Value="#EEEEEE" />
  </Trigger>
 
  <MultiTrigger>
    <MultiTrigger.Conditions>
      <Condition Property="HasItems" Value="false" />
      <Condition Property="Width" Value="Auto" />
    </MultiTrigger.Conditions>