From 2b857aba9acd1920da28cfb515e8efc9ce3ca80a Mon Sep 17 00:00:00 2001
From: Corvin <corvinszimion@googlemail.com>
Date: Tue, 23 Sep 2025 19:31:42 +0200
Subject: [PATCH 1/2] Prefer TemplateBinding over Binding with RelativeSource

---
 .../Themes/MaterialDesignTheme.Expander.xaml                    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Expander.xaml b/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Expander.xaml
index 4403d023ee..0c97ac401e 100644
--- a/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Expander.xaml
+++ b/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Expander.xaml
@@ -316,7 +316,7 @@
                       HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                       VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
                   <Grid.LayoutTransform>
-                    <RotateTransform Angle="{Binding Path=ExpandDirection, RelativeSource={RelativeSource AncestorType=Expander}, Converter={x:Static convertersInternal:ExpanderRotateAngleConverter.Instance}, ConverterParameter=-1}" />
+                    <RotateTransform Angle="{TemplateBinding ExpandDirection, Converter={x:Static convertersInternal:ExpanderRotateAngleConverter.Instance}, ConverterParameter=-1}" />
                   </Grid.LayoutTransform>
 
                   <ContentPresenter Name="PART_Content"

From a35b32cad1b033ad8b498f72516bbf971a33d276 Mon Sep 17 00:00:00 2001
From: Kevin Bost <kitokeboo@gmail.com>
Date: Thu, 25 Sep 2025 23:09:22 -0700
Subject: [PATCH 2/2] Updates Expander control template

Changes `ContentSite` border to be unnamed and binds `ExpandDirection` directly from the `TemplateBinding`.
---
 .../Themes/MaterialDesignTheme.Expander.xaml                  | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Expander.xaml b/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Expander.xaml
index 0c97ac401e..8db2533441 100644
--- a/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Expander.xaml
+++ b/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Expander.xaml
@@ -303,11 +303,11 @@
                             Opacity="0.87"
                             TextElement.FontSize="{TemplateBinding wpf:ExpanderAssist.HeaderFontSize}" />
 
-              <Border Name="ContentSite">
+              <Border>
                 <Border.LayoutTransform>
                   <TransformGroup>
                     <ScaleTransform x:Name="ContentSiteScaleTransform" />
-                    <RotateTransform Angle="{Binding Path=ExpandDirection, RelativeSource={RelativeSource AncestorType=Expander}, Converter={x:Static convertersInternal:ExpanderRotateAngleConverter.Instance}}" />
+                    <RotateTransform Angle="{TemplateBinding ExpandDirection, Converter={x:Static convertersInternal:ExpanderRotateAngleConverter.Instance}}" />
                   </TransformGroup>
                 </Border.LayoutTransform>