avoid crash on expander

Author: licanhua

dev/Expander/Expander.vcxitems

@@ -30,7 +30,12 @@
       <Type>DefaultStyle</Type>
     </Page>
     <Page Include="$(MSBuildThisFileDirectory)Expander_themeresources.xaml">
-      <UseVisualStyle>Any</UseVisualStyle>
+      <UseVisualStyle>Latest</UseVisualStyle>
+      <Version>RS1</Version>
+      <Type>ThemeResources</Type>
+    </Page>
+    <Page Include="$(MSBuildThisFileDirectory)Expander_themeresources_v2.5.xaml">
+      <UseVisualStyle>V2dot5</UseVisualStyle>
       <Version>RS1</Version>
       <Type>ThemeResources</Type>
     </Page>

dev/Expander/Expander_themeresources_v2.5.xaml

@@ -0,0 +1,32 @@
+<!-- Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT License. See LICENSE in the project root for license information. -->
+<ResourceDictionary
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:Microsoft.UI.Xaml.Controls">
+
+    <ResourceDictionary.ThemeDictionaries>
+        <ResourceDictionary x:Key="Dark">
+            <StaticResource x:Key="ExpanderHeaderBackground" ResourceKey="SystemControlTransparentBrush" />
+            <StaticResource x:Key="ExpanderChevronBackground" ResourceKey="SystemControlTransparentBrush" />
+            <StaticResource x:Key="ExpanderChevronForeground" ResourceKey="SystemControlForegroundBaseHighBrush" />
+        </ResourceDictionary>
+
+        <ResourceDictionary x:Key="Light">
+            <StaticResource x:Key="ExpanderHeaderBackground" ResourceKey="SystemControlTransparentBrush" />
+            <StaticResource x:Key="ExpanderChevronBackground" ResourceKey="SystemControlTransparentBrush" />
+            <StaticResource x:Key="ExpanderChevronForeground" ResourceKey="SystemControlForegroundBaseHighBrush" />
+        </ResourceDictionary>
+
+        <ResourceDictionary x:Key="HighContrast">
+            <StaticResource x:Key="ExpanderHeaderBackground" ResourceKey="SystemControlTransparentBrush" />
+            <StaticResource x:Key="ExpanderChevronBackground" ResourceKey="SystemControlTransparentBrush" />
+            <StaticResource x:Key="ExpanderChevronForeground" ResourceKey="SystemControlForegroundBaseHighBrush" />
+        </ResourceDictionary>
+    </ResourceDictionary.ThemeDictionaries>
+    
+    <Thickness x:Key="ExpanderChevronMargin">8</Thickness>
+    <x:String x:Key="ExpanderChevronGlyph">&#xE70D;</x:String>
+    <x:Double x:Key="ExpanderChevronWidth">40</x:Double>
+    <x:Double x:Key="ExpanderPopinVerticalOffset">50</x:Double>
+
+</ResourceDictionary>