diff --git a/eng/resolveContract.targets b/eng/resolveContract.targets
index 4a2b0a5adfcbd6..0aaf56d0a9731e 100644
--- a/eng/resolveContract.targets
+++ b/eng/resolveContract.targets
@@ -20,6 +20,17 @@
     <HasMatchingContract Condition="'$(HasMatchingContract)' == '' and Exists('$(ContractProject)')">true</HasMatchingContract>
     <!-- Disable API compat if the project doesn't have reference assembly -->
     <RunApiCompat Condition="'$(HasMatchingContract)' != 'true'">false</RunApiCompat>
+    <!-- Don't build against reference assemblies when projects are packable and the tfm is not the latest .NETCoreApp as
+         such reference assemblies don't ship to customers and only exist for tooling scenarios. -->
+    <AnnotateTargetPathWithContract Condition="'$(AnnotateTargetPathWithContract)' == '' and
+                                               '$(HasMatchingContract)' == 'true' and
+                                               (
+                                                '$(IsPackable)' != 'true' or
+                                                (
+                                                 '$(TargetFrameworkIdentifier)' == '.NETCoreApp' and
+                                                 '$(TargetFrameworkVersion)' == 'v$(NetCoreAppCurrentVersion)'
+                                                )
+                                               )">true</AnnotateTargetPathWithContract>
   </PropertyGroup>
 
   <ItemGroup Condition="'$(IsSourceProject)' == 'true' or '$(IsReferenceAssemblyProject)' == 'true' or '$(IsPartialFacadeAssembly)' == 'true'">
@@ -36,7 +47,7 @@
 
   <!-- Allow P2Ps that target a source project to build against the corresponding ref project. -->
   <Target Name="AnnotateTargetPathWithTargetPlatformMonikerWithReferenceAssembly"
-          Condition="'$(HasMatchingContract)' == 'true'"
+          Condition="'$(AnnotateTargetPathWithContract)' == 'true'"
           DependsOnTargets="ResolveProjectReferences"
           AfterTargets="GetTargetPathWithTargetPlatformMoniker">
     <ItemGroup>
diff --git a/src/libraries/System.DirectoryServices/src/ILLink/ILLink.Suppressions.xml b/src/libraries/System.DirectoryServices/src/ILLink/ILLink.Suppressions.xml
index ca9681a8e8f63b..b27ed192851d2f 100644
--- a/src/libraries/System.DirectoryServices/src/ILLink/ILLink.Suppressions.xml
+++ b/src/libraries/System.DirectoryServices/src/ILLink/ILLink.Suppressions.xml
@@ -5,7 +5,7 @@
       <argument>ILLink</argument>
       <argument>IL2050</argument>
       <property name="Scope">member</property>
-      <property name="Target">M:System.DirectoryServices.Interop.UnsafeNativeMethods.ADsOpenObject(System.String,System.String,System.String,System.Int32,System.Guid@,System.Object@)</property>
+      <property name="Target">M:System.DirectoryServices.UnsafeNativeMethods.ADsOpenObject(System.String,System.String,System.String,System.Int32,System.Guid@,System.Object@)</property>
     </attribute>
     <attribute fullname="System.Diagnostics.CodeAnalysis.UnconditionalSuppressMessageAttribute">
       <argument>ILLink</argument>
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsOptions.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsOptions.cs
index fe0ad8b59edce1..d69988da76d4fa 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsOptions.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsOptions.cs
@@ -1,7 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     internal enum AdsOptions
     {
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsPropertyOperation.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsPropertyOperation.cs
index 4d5baf7145e79c..51e3ca30f7e91d 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsPropertyOperation.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsPropertyOperation.cs
@@ -1,7 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     internal enum AdsPropertyOperation
     {
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsSearchColumn.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsSearchColumn.cs
index 76dca56431ad3c..eec178f3802bbc 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsSearchColumn.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsSearchColumn.cs
@@ -3,7 +3,7 @@
 
 using System.Runtime.InteropServices;
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     [StructLayout(LayoutKind.Sequential)]
     internal unsafe struct AdsSearchColumn
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsSearchPreferenceInfo.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsSearchPreferenceInfo.cs
index e1b5936c71fd35..0e8c328615446f 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsSearchPreferenceInfo.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsSearchPreferenceInfo.cs
@@ -3,7 +3,7 @@
 
 using System.Runtime.InteropServices;
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     [StructLayout(LayoutKind.Sequential)]
     internal struct AdsSearchPreferenceInfo
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsSearchPreferences.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsSearchPreferences.cs
index ec409e3a53c309..dd4df804005e0d 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsSearchPreferences.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsSearchPreferences.cs
@@ -1,7 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     internal enum AdsSearchPreferences
     {
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsSortKey.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsSortKey.cs
index 1c844d7741c979..b25a14b9a29cf7 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsSortKey.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsSortKey.cs
@@ -3,7 +3,7 @@
 
 using System.Runtime.InteropServices;
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     [StructLayout(LayoutKind.Sequential)]
     internal struct AdsSortKey
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsType.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsType.cs
index 7320c9d512cb4b..2c1d54779ab44c 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsType.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsType.cs
@@ -1,7 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     internal enum AdsType
     {
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsValue2.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsValue2.cs
index 82c2413f1ec716..5aa77b9ea7c95f 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsValue2.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsValue2.cs
@@ -3,7 +3,7 @@
 
 using System.Runtime.InteropServices;
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     [StructLayout(LayoutKind.Sequential)]
     internal struct Ads_Pointer
diff --git a/src/libraries/System.DirectoryServices/src/Interop/AdsValueHelper2.cs b/src/libraries/System.DirectoryServices/src/Interop/AdsValueHelper2.cs
index 10b208f0784ccf..3a19d778c24644 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/AdsValueHelper2.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/AdsValueHelper2.cs
@@ -5,7 +5,7 @@
 using System.Runtime.InteropServices;
 using System.Globalization;
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     [StructLayout(LayoutKind.Sequential)]
     internal struct SystemTime
diff --git a/src/libraries/System.DirectoryServices/src/Interop/NativeMethods.cs b/src/libraries/System.DirectoryServices/src/Interop/NativeMethods.cs
index 7ce5748edbc6c7..ca45d792515d66 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/NativeMethods.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/NativeMethods.cs
@@ -1,7 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     internal static class NativeMethods
     {
diff --git a/src/libraries/System.DirectoryServices/src/Interop/SafeNativeMethods.cs b/src/libraries/System.DirectoryServices/src/Interop/SafeNativeMethods.cs
index db401906f69eea..9ae1fdfd26811c 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/SafeNativeMethods.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/SafeNativeMethods.cs
@@ -5,7 +5,7 @@
 using System.Security;
 using System.Runtime.InteropServices;
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
     internal static partial class SafeNativeMethods
     {
diff --git a/src/libraries/System.DirectoryServices/src/Interop/UnsafeNativeMethods.cs b/src/libraries/System.DirectoryServices/src/Interop/UnsafeNativeMethods.cs
index 30912155a31fc5..b6f6e72aad9bd2 100644
--- a/src/libraries/System.DirectoryServices/src/Interop/UnsafeNativeMethods.cs
+++ b/src/libraries/System.DirectoryServices/src/Interop/UnsafeNativeMethods.cs
@@ -5,7 +5,7 @@
 using System.Runtime.InteropServices;
 using System.Security;
 
-namespace System.DirectoryServices.Interop
+namespace System.DirectoryServices
 {
 
     [StructLayout(LayoutKind.Explicit)]
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/ActiveDirectory/DomainController.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/ActiveDirectory/DomainController.cs
index 98eb7d72044970..0a855c618d928c 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/ActiveDirectory/DomainController.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/ActiveDirectory/DomainController.cs
@@ -410,7 +410,7 @@ public void SeizeRoleOwnership(ActiveDirectoryRole role)
                 // Increment the RIDAvailablePool by 30k.
                 if (role == ActiveDirectoryRole.RidRole)
                 {
-                    System.DirectoryServices.Interop.UnsafeNativeMethods.IADsLargeInteger ridPool = (System.DirectoryServices.Interop.UnsafeNativeMethods.IADsLargeInteger)roleObjectEntry.Properties[PropertyManager.RIDAvailablePool].Value!;
+                    System.DirectoryServices.UnsafeNativeMethods.IADsLargeInteger ridPool = (System.DirectoryServices.UnsafeNativeMethods.IADsLargeInteger)roleObjectEntry.Properties[PropertyManager.RIDAvailablePool].Value!;
 
                     // check the overflow of the low part
                     if (ridPool.LowPart + UpdateRidPoolSeizureValue < ridPool.LowPart)
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/AuthenticationTypes.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/AuthenticationTypes.cs
index 0a7ece6d9ddb17..f44e180c4c384f 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/AuthenticationTypes.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/AuthenticationTypes.cs
@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.DirectoryServices.Interop;
-
 namespace System.DirectoryServices
 {
     /// <devdoc>
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntries.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntries.cs
index 71d53ef6901198..cb2082a0f1ffbd 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntries.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntries.cs
@@ -3,7 +3,6 @@
 
 using System.Runtime.InteropServices;
 using System.Collections;
-using System.DirectoryServices.Interop;
 
 namespace System.DirectoryServices
 {
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntry.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntry.cs
index 429c4a4f779e80..c4d046cf006568 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntry.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntry.cs
@@ -3,7 +3,6 @@
 
 using System.Runtime.InteropServices;
 using System.Diagnostics;
-using System.DirectoryServices.Interop;
 using System.ComponentModel;
 using System.Threading;
 using System.Reflection;
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntryConfiguration.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntryConfiguration.cs
index df98c453502818..1ff7fcb1e3d2a4 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntryConfiguration.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryEntryConfiguration.cs
@@ -1,7 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.DirectoryServices.Interop;
 using System.ComponentModel;
 
 namespace System.DirectoryServices
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectorySearcher.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectorySearcher.cs
index 846fffa58e4f2b..1ef524342a3357 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectorySearcher.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectorySearcher.cs
@@ -4,7 +4,6 @@
 using System.Runtime.InteropServices;
 using System.Collections;
 using System.Collections.Specialized;
-using System.DirectoryServices.Interop;
 using System.ComponentModel;
 
 using INTPTR_INTPTRCAST = System.IntPtr;
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesCOMException.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesCOMException.cs
index ac1ee821b1c46d..6ff6d88c562415 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesCOMException.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesCOMException.cs
@@ -4,7 +4,6 @@
 using System.ComponentModel;
 using System.Runtime.InteropServices;
 using System.Runtime.Serialization;
-using System.DirectoryServices.Interop;
 
 namespace System.DirectoryServices
 {
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/PropertyCollection.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/PropertyCollection.cs
index 51878e2cc52d1e..38d202f7053640 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/PropertyCollection.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/PropertyCollection.cs
@@ -3,7 +3,6 @@
 
 using System.Runtime.InteropServices;
 using System.Collections;
-using System.DirectoryServices.Interop;
 using System.Globalization;
 
 namespace System.DirectoryServices
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/PropertyValueCollection.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/PropertyValueCollection.cs
index 4ae15eb0b7a9d5..a006b65e7e4bbf 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/PropertyValueCollection.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/PropertyValueCollection.cs
@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections;
-using System.DirectoryServices.Interop;
 
 namespace System.DirectoryServices
 {
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/SchemaNameCollection.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/SchemaNameCollection.cs
index 853c659ecfd88d..7acb9bf62334e7 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/SchemaNameCollection.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/SchemaNameCollection.cs
@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections;
-using System.DirectoryServices.Interop;
 
 namespace System.DirectoryServices
 {
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/SearchResultCollection.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/SearchResultCollection.cs
index 4711b60e97b54c..dac7ae1f9f7542 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/SearchResultCollection.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/SearchResultCollection.cs
@@ -4,7 +4,6 @@
 using System.Net;
 using System.Runtime.InteropServices;
 using System.Collections;
-using System.DirectoryServices.Interop;
 using System.Text;
 
 using INTPTR_INTPTRCAST = System.IntPtr;
diff --git a/src/libraries/System.Runtime.Serialization.Schema/src/System/Runtime/Serialization/Schema/CodeExporter.cs b/src/libraries/System.Runtime.Serialization.Schema/src/System/Runtime/Serialization/Schema/CodeExporter.cs
index 45476be4423f10..78a0301fe3ad50 100644
--- a/src/libraries/System.Runtime.Serialization.Schema/src/System/Runtime/Serialization/Schema/CodeExporter.cs
+++ b/src/libraries/System.Runtime.Serialization.Schema/src/System/Runtime/Serialization/Schema/CodeExporter.cs
@@ -520,8 +520,8 @@ private static CodeTypeDeclaration CreateTypeDeclaration(string typeName, DataCo
             CodeAttributeDeclaration generatedCodeAttribute = new CodeAttributeDeclaration(typeof(GeneratedCodeAttribute).FullName!);
 
             AssemblyName assemblyName = Assembly.GetExecutingAssembly().GetName();
-            generatedCodeAttribute.Arguments.Add(new CodeAttributeArgument(new CodePrimitiveExpression(assemblyName.Name)));
-            generatedCodeAttribute.Arguments.Add(new CodeAttributeArgument(new CodePrimitiveExpression(assemblyName.Version?.ToString())));
+            generatedCodeAttribute.Arguments.Add(new CodeAttributeArgument(new CodePrimitiveExpression(assemblyName.Name!)));
+            generatedCodeAttribute.Arguments.Add(new CodeAttributeArgument(new CodePrimitiveExpression(assemblyName.Version?.ToString()!)));
 
             // System.Diagnostics.DebuggerStepThroughAttribute not allowed on enums
             // ensure that the attribute is only generated on types that are not enums
@@ -820,7 +820,7 @@ private void ExportClassDataContract(DataContract classDataContract, ContractCod
             {
                 ContractCodeDomInfo baseContractCodeDomInfo = GetContractCodeDomInfo(classDataContract.BaseContract);
                 Debug.Assert(baseContractCodeDomInfo.IsProcessed, "Cannot generate code for type if code for base type has not been generated");
-                type.BaseTypes.Add(baseContractCodeDomInfo.TypeReference);
+                type.BaseTypes.Add(baseContractCodeDomInfo.TypeReference!);
                 AddBaseMemberNames(baseContractCodeDomInfo, contractCodeDomInfo);
                 if (baseContractCodeDomInfo.ReferencedTypeExists)
                 {
@@ -1153,7 +1153,7 @@ private void ExportISerializableDataContract(DataContract classDataContract, Con
             {
                 ContractCodeDomInfo baseContractCodeDomInfo = GetContractCodeDomInfo(classDataContract.BaseContract);
                 GenerateType(classDataContract.BaseContract, baseContractCodeDomInfo);
-                type.BaseTypes.Add(baseContractCodeDomInfo.TypeReference);
+                type.BaseTypes.Add(baseContractCodeDomInfo.TypeReference!);
                 if (baseContractCodeDomInfo.ReferencedTypeExists)
                 {
                     Type? actualType = (Type?)baseContractCodeDomInfo.TypeReference?.UserData[s_codeUserDataActualTypeKey];
@@ -1238,7 +1238,7 @@ private void ExportCollectionDataContract(DataContract collectionContract, Contr
             Debug.Assert(contractCodeDomInfo.TypeDeclaration != null);
 
             CodeTypeDeclaration generatedType = contractCodeDomInfo.TypeDeclaration;
-            generatedType.BaseTypes.Add(baseTypeReference);
+            generatedType.BaseTypes.Add(baseTypeReference!);
             CodeAttributeDeclaration collectionContractAttribute = new CodeAttributeDeclaration(GetClrTypeFullName(typeof(CollectionDataContractAttribute)));
             collectionContractAttribute.Arguments.Add(new CodeAttributeArgument(ImportGlobals.NameProperty, new CodePrimitiveExpression(dataContractName)));
             collectionContractAttribute.Arguments.Add(new CodeAttributeArgument(ImportGlobals.NamespaceProperty, new CodePrimitiveExpression(collectionContract.XmlName.Namespace)));
@@ -1673,7 +1673,7 @@ private static CodeThisReferenceExpression ThisReference
 
         private static CodePrimitiveExpression NullReference
         {
-            get { return new CodePrimitiveExpression(null); }
+            get { return new CodePrimitiveExpression(null!); }
         }
 
         private CodeParameterDeclarationExpression SerializationInfoParameter
@@ -1784,12 +1784,12 @@ private CodeMemberMethod GetSchemaStaticMethod
                         new CodeTypeReferenceExpression(GetCodeTypeReference(typeof(XmlSerializableServices))),
                         nameof(XmlSerializableServices.AddDefaultSchema),
                         new CodeArgumentReferenceExpression(paramDeclaration.Name),
-                        new CodeFieldReferenceExpression(null, TypeNameFieldName)
+                        new CodeFieldReferenceExpression(null!, TypeNameFieldName)
                     )
                 );
                 getSchemaStaticMethod.Statements.Add(
                     new CodeMethodReturnStatement(
-                        new CodeFieldReferenceExpression(null, TypeNameFieldName)
+                        new CodeFieldReferenceExpression(null!, TypeNameFieldName)
                     )
                 );
                 return getSchemaStaticMethod;