更新

WPFDark/Internals/SharedResourceDictionary.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Windows;
+
+namespace WPFDark.Internals
+{
+    public class SharedResourceDictionary : ResourceDictionary
+    {
+        private static readonly Dictionary<int, ResourceDictionary> _sharedDictionaries = new Dictionary<int, ResourceDictionary>();
+
+        private static readonly bool _isInDesignerMode;
+
+        private Uri? _sourceUri;
+
+        static SharedResourceDictionary()
+        {
+            _isInDesignerMode = (bool) DesignerProperties.IsInDesignModeProperty.GetMetadata(typeof(DependencyObject)).DefaultValue;
+        }
+
+        public new Uri Source
+        {
+            get => _sourceUri ?? throw new NullReferenceException();
+
+            set
+            {
+                _sourceUri = value;
+
+                if (_isInDesignerMode)
+                {
+                    base.Source = value;
+                    return;
+                }
+
+                var hashCode = value.GetHashCode();
+
+                if (_sharedDictionaries.TryGetValue(hashCode, out var v) == false)
+                {
+                    base.Source = value;
+
+                    _sharedDictionaries.Add(hashCode, this);
+                }
+                else
+                {
+                    MergedDictionaries.Add(v);
+                }
+            }
+        }
+    }
+}