From f2d0cbda6c60d6ca8bc1b215713f1a191fe24659 Mon Sep 17 00:00:00 2001
From: Yimeng Wu <me@kinnara.cn>
Date: Tue, 22 Oct 2019 04:06:56 +0800
Subject: [PATCH] Avoid injecting DefaultThemeResources multiple times

---
 ModernWpf/ThemeResources.cs | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/ModernWpf/ThemeResources.cs b/ModernWpf/ThemeResources.cs
index 93fd0f76..b1d45e4e 100644
--- a/ModernWpf/ThemeResources.cs
+++ b/ModernWpf/ThemeResources.cs
@@ -290,12 +290,7 @@ private ResourceDictionary GetThemeDictionary(string key)
 
             if (ThemeDictionaries.TryGetValue(key, out ResourceDictionary themeDictionary))
             {
-                if (themeDictionary.MergedDictionaries.Count > 0 &&
-                    themeDictionary.MergedDictionaries[0] is DefaultThemeResources)
-                {
-                    // Already contains the default theme resources
-                }
-                else
+                if (!ContainsDefaultThemeResources(themeDictionary))
                 {
                     themeDictionary.MergedDictionaries.Insert(0, defaultThemeDictionary);
                 }
@@ -307,5 +302,24 @@ private ResourceDictionary GetThemeDictionary(string key)
 
             return themeDictionary;
         }
+
+        private static bool ContainsDefaultThemeResources(ResourceDictionary dictionary)
+        {
+            if (dictionary is DefaultThemeResources)
+            {
+                return true;
+            }
+
+            foreach (var mergedDictionary in dictionary.MergedDictionaries)
+            {
+                if (mergedDictionary is DefaultThemeResources ||
+                    mergedDictionary != null && ContainsDefaultThemeResources(mergedDictionary))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
     }
 }