Shaker/Avalonia/SukiUI/Theme/AutoCompleteBoxStyles.axaml

<ResourceDictionary xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Design.PreviewWith>
        <Border Width="300"
                Padding="20"
                Background="{DynamicResource SukiBackground}">
            <StackPanel>
                <AutoCompleteBox />


            </StackPanel>
        </Border>
    </Design.PreviewWith>
    <ControlTheme x:Key="{x:Type AutoCompleteBox}" TargetType="AutoCompleteBox">
        <Setter Property="BorderThickness" Value="0,0,0,1" />
        <Setter Property="MinWidth" Value="100" />
        <Setter Property="BorderBrush" Value="{DynamicResource SukiControlBorderBrush}" />
        <Setter Property="CornerRadius" Value="0" />
        <Setter Property="Background" Value="{DynamicResource SukiBackground}" />
        <Setter Property="Padding" Value="4" />
        <Setter Property="Template">
            <ControlTemplate>
                <Panel>
                    <TextBox Name="PART_TextBox"
                             Padding="{TemplateBinding Padding}"
                             Background="{TemplateBinding Background}"
                             BorderBrush="{TemplateBinding BorderBrush}"
                             BorderThickness="{TemplateBinding BorderThickness}"
                             CornerRadius="{TemplateBinding CornerRadius}"
                             DataValidationErrors.Errors="{TemplateBinding (DataValidationErrors.Errors)}"
                             Watermark="{TemplateBinding Watermark}" />

                    <Popup Name="PART_Popup"
                           MinWidth="{Binding Bounds.Width, RelativeSource={RelativeSource TemplatedParent}}"
                           MaxHeight="{TemplateBinding MaxDropDownHeight}"
                           IsLightDismissEnabled="True"
                           PlacementTarget="{TemplateBinding}">
                        <Border Margin="0,-15,0,0" Padding="5,10,5,5">
                            <Panel>
                                <Border Margin="0,10,0,0"
                                        Background="{DynamicResource SukiCardBackground}"
                                        BorderBrush="{DynamicResource SukiControlBorderBrush}"
                                        BorderThickness="1,1,1,1"
                                        BoxShadow="{DynamicResource SukiPopupShadow}"
                                        CornerRadius="{DynamicResource SmallCornerRadius}">
                                    <Panel Background="{DynamicResource PopupGradientBrush}">
                                    <ListBox Name="PART_SelectingItemsControl"
                                             Background="{TemplateBinding Background}"
                                             BorderThickness="0"
                                             Foreground="{TemplateBinding Foreground}"
                                             ItemTemplate="{TemplateBinding ItemTemplate}"
                                             ScrollViewer.HorizontalScrollBarVisibility="Auto"
                                             ScrollViewer.VerticalScrollBarVisibility="Auto" />
                                    </Panel>
                                </Border>
                            </Panel>
                        </Border>
                    </Popup>
                </Panel>
            </ControlTemplate>
        </Setter>
    </ControlTheme>
</ResourceDictionary>