diff --git a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/Assembly.mustache b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/Assembly.mustache
new file mode 100644
index 00000000000..a22cc2326b2
--- /dev/null
+++ b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/Assembly.mustache
@@ -0,0 +1,2 @@
+[assembly: InternalsVisibleTo("{{packageName}}.Test")]
+
diff --git a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
index a8a92172aaf..47d4b4c26f2 100644
--- a/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
+++ b/modules/openapi-generator/src/main/resources/csharp/libraries/generichost/ClientUtils.mustache
@@ -13,8 +13,9 @@ using System.Text.Json;
 using System.Text.RegularExpressions;{{#useCompareNetObjects}}
 using KellermanSoftware.CompareNetObjects;{{/useCompareNetObjects}}
 using {{packageName}}.{{modelPackage}};
+using System.Runtime.CompilerServices;
 
-namespace {{packageName}}.{{clientPackage}}
+{{>Assembly}}namespace {{packageName}}.{{clientPackage}}
 {
     /// <summary>
     /// Utility functions providing some benefit to API client consumers.
diff --git a/samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0-nrt/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0-nrt/src/Org.OpenAPITools/Client/ClientUtils.cs
index b38f735ae16..d76afebed11 100644
--- a/samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0-nrt/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0-nrt/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,9 @@ using System.Text.Json;
 using System.Text.RegularExpressions;
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
 namespace Org.OpenAPITools.Client
 {
diff --git a/samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0/src/Org.OpenAPITools/Client/ClientUtils.cs
index 7769e9200eb..b09cb7f69ec 100644
--- a/samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient-generichost-net6.0/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -17,6 +17,9 @@ using System.Text.Json;
 using System.Text.RegularExpressions;
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
 namespace Org.OpenAPITools.Client
 {
diff --git a/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-allOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-allOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index d8a9f0ca4a0..083d9d9ea80 100644
--- a/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-allOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-allOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,9 @@ using System.Text.Json;
 using System.Text.RegularExpressions;
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
 namespace Org.OpenAPITools.Client
 {
diff --git a/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-anyOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-anyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 6eb7acc88f4..8908d5c5d96 100644
--- a/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-anyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-anyOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,9 @@ using System.Text.Json;
 using System.Text.RegularExpressions;
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
 namespace Org.OpenAPITools.Client
 {
diff --git a/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-oneOf/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-oneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
index 6eb7acc88f4..8908d5c5d96 100644
--- a/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-oneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient-generichost-netcore-latest-oneOf/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -19,6 +19,9 @@ using System.Text.Json;
 using System.Text.RegularExpressions;
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
 namespace Org.OpenAPITools.Client
 {
diff --git a/samples/client/petstore/csharp/OpenAPIClient-generichost-netstandard2.0/src/Org.OpenAPITools/Client/ClientUtils.cs b/samples/client/petstore/csharp/OpenAPIClient-generichost-netstandard2.0/src/Org.OpenAPITools/Client/ClientUtils.cs
index c5906786632..5e1beb8d054 100644
--- a/samples/client/petstore/csharp/OpenAPIClient-generichost-netstandard2.0/src/Org.OpenAPITools/Client/ClientUtils.cs
+++ b/samples/client/petstore/csharp/OpenAPIClient-generichost-netstandard2.0/src/Org.OpenAPITools/Client/ClientUtils.cs
@@ -17,6 +17,9 @@ using System.Text.Json;
 using System.Text.RegularExpressions;
 using KellermanSoftware.CompareNetObjects;
 using Org.OpenAPITools.Model;
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Org.OpenAPITools.Test")]
 
 namespace Org.OpenAPITools.Client
 {