<Application.Resources>
     <ResourceDictionary>
         <ResourceDictionary.MergedDictionaries>
             <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
			 <ResourceDictionary Source="ms-appx:///Telerik.WinUI.Controls/Themes/Generic.xaml"/>
			 <!-- Other merged dictionaries here -->
         </ResourceDictionary.MergedDictionaries>
			<!-- Other app resources here -->

		<Style  TargetType="chat:ChatMessageList" BasedOn="{StaticResource ChatMessageListStyle}">
			<Setter Property="Template">
				<Setter.Value>
					<ControlTemplate TargetType="chat:ChatMessageList">
						<Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
							<!--The background of the Scrollviewer is set here-->
							<ScrollViewer x:Name="PART_ScrollViewer" 
										  VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Disabled" 
										  BorderThickness="0"
										  Background="Transparent">
								<ItemsPresenter Margin="{TemplateBinding Padding}" />
							</ScrollViewer>
						</Border>
					</ControlTemplate>
				</Setter.Value>
			</Setter>
		</Style>
	</ResourceDictionary>
 </Application.Resources>