Demo_Validation/App.axaml

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="AvaloniaValidationSample.App"
             RequestedThemeVariant="Default">
	<!-- "Default" ThemeVariant follows system theme variant. "Dark" or "Light" are other available options. -->

	<Application.Styles>
		<FluentTheme />
	</Application.Styles>
</Application>