Wrote some black magic due to this bug https://github.com/windows-toolkit/Microsoft.Toolkit.Win32/issues/228

NotificationFlyout.Sample/NotificationFlyoutPresenter.xaml

@@ -2,13 +2,15 @@
     x:Class="NotificationFlyout.Sample.NotificationFlyoutPresenter"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-    xmlns:controls="using:NotificationFlyout.Uwp.UI.Controls"
-    CornerRadius="4"
-    RequestedTheme="Default">
+    xmlns:controls="using:NotificationFlyout.Uwp.UI.Controls">
     <Grid
         Width="330"
         Height="360"
-        Margin="23">
-        <ToggleSwitch x:Name="test" Toggled="ToggleSwitch_Toggled" />
+        Margin="24">
+        <ComboBox x:Name="test" Margin="0,0,0,8" SelectionChanged="test_SelectionChanged">
+            <ComboBoxItem>System</ComboBoxItem>
+            <ComboBoxItem>Dark</ComboBoxItem>
+            <ComboBoxItem>Light</ComboBoxItem>
+        </ComboBox>
     </Grid>
 </controls:NotificationFlyoutPresenter>

NotificationFlyout.Sample/NotificationFlyoutPresenter.xaml.cs

@@ -7,13 +7,21 @@
             InitializeComponent();
         }
 
-        private void ToggleSwitch_Toggled(object sender, Windows.UI.Xaml.RoutedEventArgs e)
+        private void test_SelectionChanged(object sender, Windows.UI.Xaml.Controls.SelectionChangedEventArgs e)
         {
-            if (test.IsOn)
+            if (test.SelectedIndex == 0)
+            {
+                this.RequestedTheme = Windows.UI.Xaml.ElementTheme.Default;
+
+            }
+
+            if (test.SelectedIndex == 1)
             {
                 this.RequestedTheme = Windows.UI.Xaml.ElementTheme.Dark;
+
             }
-            else
+
+            if (test.SelectedIndex == 2)
             {
                 this.RequestedTheme = Windows.UI.Xaml.ElementTheme.Light;
 

NotificationFlyout.Sample/Properties/AssemblyInfo.cs

@@ -14,7 +14,8 @@ using System.Runtime.InteropServices;
 [assembly: AssemblyTrademark("")]
 [assembly: AssemblyCulture("")]
 
-// Version information for an assembly consists of the following four values:
+//
+// information for an assembly consists of the following four values:
 //
 //      Major Version
 //      Minor Version