diff --git a/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/ObjectWriterContext.cs b/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/ObjectWriterContext.cs
index 6057278ab35..21af3d22cf9 100644
--- a/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/ObjectWriterContext.cs
+++ b/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/ObjectWriterContext.cs
@@ -205,22 +205,6 @@ internal IEnumerable<AmbientPropertyValue> ServiceProvider_GetAllAmbientValues(I
             return valueList;
         }
 
-        private static void CheckAmbient(XamlMember xamlMember)
-        {
-            if (!xamlMember.IsAmbient)
-            {
-                throw new ArgumentException(SR.Get(SRID.NotAmbientProperty, xamlMember.DeclaringType.Name, xamlMember.Name), nameof(xamlMember));
-            }
-        }
-
-        private static void CheckAmbient(XamlType xamlType)
-        {
-            if (!xamlType.IsAmbient)
-            {
-                throw new ArgumentException(SR.Get(SRID.NotAmbientType, xamlType.Name), nameof(xamlType));
-            }
-        }
-
         internal XamlObjectWriterSettings ServiceProvider_GetSettings()
         {
             if (_settings == null)
@@ -326,8 +310,15 @@ private List<AmbientPropertyValue> FindAmbientValues(IEnumerable<XamlType> ceili
                                                              XamlMember[] properties,
                                                              bool stopAfterFirst)
         {
-            ArrayHelper.ForAll<XamlMember>(properties, CheckAmbient);
-            List<XamlType> ceilingTypes = ArrayHelper.ToList<XamlType>(ceilingTypesEnumerable);
+            foreach (XamlMember xamlMember in properties)
+            {
+                if (!xamlMember.IsAmbient)
+                {
+                    throw new ArgumentException(SR.Get(SRID.NotAmbientProperty, xamlMember.DeclaringType.Name, xamlMember.Name), nameof(properties));
+                }
+            }
+
+            List<XamlType> ceilingTypes = ceilingTypesEnumerable != null ? new List<XamlType>(ceilingTypesEnumerable) : null;
 
             List<AmbientPropertyValue> retList = new List<AmbientPropertyValue>();
 
@@ -436,13 +427,18 @@ private List<AmbientPropertyValue> FindAmbientValues(IEnumerable<XamlType> ceili
 
         private List<object> FindAmbientValues(XamlType[] types, bool stopAfterFirst)
         {
-            ArrayHelper.ForAll<XamlType>(types, CheckAmbient);
+            foreach (XamlType xamlType in types)
+            {
+                if (!xamlType.IsAmbient)
+                {
+                    throw new ArgumentException(SR.Get(SRID.NotAmbientType, xamlType.Name), nameof(types));
+                }
+            }
 
             List<object> retList = new List<object>();
 
             // Start the search for ambient properties with the parent frame.
             ObjectWriterFrame frame = _stack.PreviousFrame;
-            ObjectWriterFrame lowerFrame = _stack.CurrentFrame;
 
             while (frame.Depth >= 1)
             {
@@ -463,7 +459,6 @@ private List<object> FindAmbientValues(XamlType[] types, bool stopAfterFirst)
                     }
                 }
 
-                lowerFrame = frame;
                 frame = (ObjectWriterFrame)frame.Previous;
                 Debug.Assert(frame != null);
             }
diff --git a/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/XamlContext.cs b/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/XamlContext.cs
index 431fa56ef5b..1f62a6cdfae 100644
--- a/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/XamlContext.cs
+++ b/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/XamlContext.cs
@@ -268,8 +268,12 @@ internal XamlType GetXamlType(XamlTypeName typeName, bool returnUnknownTypesOnFa
                 XamlType[] typeArgs = null;
                 if (typeName.HasTypeArgs)
                 {
-                    typeArgs = ArrayHelper.ConvertArrayType<XamlTypeName, XamlType>(
-                        typeName.TypeArguments, GetXamlTypeOrUnknown);
+                    List<XamlTypeName> typeNames = typeName.TypeArgumentsList;
+                    typeArgs = new XamlType[typeNames.Count];
+                    for (int i = 0; i < typeArgs.Length; i++)
+                    {
+                        typeArgs[i] = GetXamlTypeOrUnknown(typeNames[i]);
+                    }
                 }
                 xamlType = new XamlType(typeName.Namespace, typeName.Name, typeArgs, SchemaContext);
             }
diff --git a/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/MS/Impl/ArrayHelper.cs b/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/MS/Impl/ArrayHelper.cs
deleted file mode 100644
index 7ca0c95091e..00000000000
--- a/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/MS/Impl/ArrayHelper.cs
+++ /dev/null
@@ -1,39 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System.Collections.Generic;
-
-namespace System.Xaml
-{
-    internal static class ArrayHelper
-    {
-        internal static S[] ConvertArrayType<R, S>(ICollection<R> src, Func<R, S> f)
-        {
-            if (src == null)
-            {
-                return null;
-            }
-            int len = src.Count, n = 0;
-            S[] dest = new S[len];
-            foreach (R r in src)
-            {
-                dest[n++] = f(r);
-            }
-            return dest;
-        }
-
-        internal static void ForAll<R>(R[] src, Action<R> f) 
-        {
-            foreach (R r in src)
-                f(r);
-        }
-
-        internal static List<T> ToList<T>(IEnumerable<T> src)
-        {
-            return (src != null)
-                ? new List<T>(src)
-                : null;
-        }
-    }
-}
diff --git a/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlTypeName.cs b/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlTypeName.cs
index 3aa8be55c17..2081c71bb50 100644
--- a/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlTypeName.cs
+++ b/src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlTypeName.cs
@@ -66,6 +66,8 @@ public IList<XamlTypeName> TypeArguments
             }
         }
 
+        internal List<XamlTypeName> TypeArgumentsList => _typeArguments;
+
         public override string ToString()
         {
             return ToString(null);