<Window.Resources>
<ControlTemplate x:Key="TextBoxBaseControlTemplate" TargetType="{x:Type TextBoxBase}">
<Border Background="{TemplateBinding Background}"
x:Name="Bd" BorderBrush="Black"
BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="10">
<ScrollViewer x:Name="PART_ContentHost"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" TargetName="Bd"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
<Trigger Property="Width" Value="Auto">
<Setter Property="MinWidth" Value="100"/>
</Trigger>
<Trigger Property="Height" Value="Auto">
<Setter Property="MinHeight" Value="20"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Window.Resources>
<Grid>
<ComboBox Template="{StaticResource TextBoxBaseControlTemplate}" Margin="144,107,253,168"/>
</Grid>
</Window>