fix: Handle types correctly in ResourceDictionary

src/Uno.UI.Tests/Windows_UI_Xaml/Given_ResourceDictionary.cs

@@ -46,6 +46,35 @@ public void When_Simple_Add_And_Retrieve()
 			Assert.AreEqual(Colors.DarkOliveGreen, ((SolidColorBrush)retrieved2).Color);
 		}
 
+		[TestMethod]
+		public void When_Simple_Add_And_Retrieve_Type_Key()
+		{
+			var rd = new ResourceDictionary();
+
+			// NOTE: Intentionally using a type outside of Uno.UI to prevent regressions if someone thought to use Type.GetType.
+			// See: https://stackoverflow.com/a/1825156/5108631
+			// Type.GetType(...) only works when the type is found in either mscorlib.dll or the currently executing assembly.
+			rd[typeof(Given_ResourceDictionary)] = nameof(When_Simple_Add_And_Retrieve_Type_Key);
+
+			var retrieved = rd[typeof(Given_ResourceDictionary)];
+
+			Assert.IsTrue(rd.ContainsKey(typeof(Given_ResourceDictionary)));
+			Assert.IsFalse(rd.ContainsKey("Uno.UI.Tests.Windows_UI_Xaml.Given_ResourceDictionary"));
+
+			Assert.AreEqual(nameof(When_Simple_Add_And_Retrieve_Type_Key), retrieved);
+
+			rd.TryGetValue(typeof(Given_ResourceDictionary), out var retrieved2);
+			Assert.AreEqual(nameof(When_Simple_Add_And_Retrieve_Type_Key), retrieved2);
+
+			var key = rd.Keys.Single();
+			Assert.AreEqual(typeof(Given_ResourceDictionary), key);
+
+			foreach (var kvp in rd)
+			{
+				Assert.AreEqual(typeof(Given_ResourceDictionary), kvp.Key);
+			}
+		}
+
 		[TestMethod]
 		public void When_Key_Not_Present()
 		{

src/Uno.UI/UI/Xaml/ResourceDictionary.cs

@@ -387,10 +387,10 @@ private void CopyFrom(ResourceDictionary source)
 		}
 
 		public global::System.Collections.Generic.ICollection<object> Keys
-			=> _values.Keys.Select(k => ConvertKey(k.Key)).ToList();
+			=> _values.Keys.Select(k => ConvertKey(k)).ToList();
 
 		private static object ConvertKey(ResourceKey resourceKey)
-			=> resourceKey.IsType ? Type.GetType(resourceKey.Key) : (object)resourceKey.Key;
+			=> resourceKey.IsType ? resourceKey.TypeKey : (object)resourceKey.Key;
 
 		// TODO: this doesn't handle lazy initializers or aliases
 		public global::System.Collections.Generic.ICollection<object> Values => _values.Values;
@@ -442,11 +442,11 @@ public IEnumerator<KeyValuePair<object, object>> GetEnumerator()
 				var aliased = kvp.Value;
 				if (TryResolveAlias(ref aliased))
 				{
-					yield return new KeyValuePair<object, object>(ConvertKey(kvp.Key.Key), aliased);
+					yield return new KeyValuePair<object, object>(ConvertKey(kvp.Key), aliased);
 				}
 				else
 				{
-					yield return new KeyValuePair<object, object>(ConvertKey(kvp.Key.Key), kvp.Value);
+					yield return new KeyValuePair<object, object>(ConvertKey(kvp.Key), kvp.Value);
 				}
 			}
 		}

src/Uno.UI/UI/Xaml/SpecializedResourceDictionary.cs

@@ -31,6 +31,7 @@ internal class SpecializedResourceDictionary
 		public readonly struct ResourceKey
 		{
 			public readonly string Key;
+			public readonly Type TypeKey;
 			public readonly bool IsType;
 			public readonly uint HashCode;
 
@@ -41,6 +42,7 @@ public readonly struct ResourceKey
 			private ResourceKey(bool dummy)
 			{
 				Key = null;
+				TypeKey = null;
 				IsType = false;
 				HashCode = 0;
 			}
@@ -54,12 +56,14 @@ public ResourceKey(object key)
 				if (key is string s)
 				{
 					Key = s;
+					TypeKey = null;
 					IsType = false;
 					HashCode = (uint)(s.GetHashCode() ^ IsType.GetHashCode());
 				}
 				else if (key is Type t)
 				{
 					Key = t.ToString();
+					TypeKey = t;
 					IsType = true;
 					HashCode = (uint)(t.GetHashCode() ^ IsType.GetHashCode());
 				}
@@ -72,6 +76,7 @@ public ResourceKey(object key)
 				else
 				{
 					Key = key.ToString();
+					TypeKey = null;
 					IsType = false;
 					HashCode = (uint)(key.GetHashCode() ^ IsType.GetHashCode());
 				}
@@ -84,6 +89,7 @@ public ResourceKey(object key)
 			public ResourceKey(string key)
 			{
 				Key = key;
+				TypeKey = null;
 				IsType = false;
 				HashCode = (uint)(key.GetHashCode() ^ IsType.GetHashCode());
 			}
@@ -95,6 +101,7 @@ public ResourceKey(string key)
 			public ResourceKey(Type key)
 			{
 				Key = key.ToString();
+				TypeKey = key;
 				IsType = true;
 				HashCode = (uint)(key.GetHashCode() ^ IsType.GetHashCode());
 			}