diff --git a/src/Microsoft.OpenApi.Hidi/Formatters/PowerShellFormatter.cs b/src/Microsoft.OpenApi.Hidi/Formatters/PowerShellFormatter.cs
index 96d3cc17d..a76dcf354 100644
--- a/src/Microsoft.OpenApi.Hidi/Formatters/PowerShellFormatter.cs
+++ b/src/Microsoft.OpenApi.Hidi/Formatters/PowerShellFormatter.cs
@@ -52,7 +52,8 @@ public override void Visit(OpenApiSchema schema)
 
         public override void Visit(OpenApiPathItem pathItem)
         {
-            if (pathItem.Operations.TryGetValue(OperationType.Put, out var value))
+            if (pathItem.Operations.TryGetValue(OperationType.Put, out var value) &&
+                value.OperationId != null)
             {
                 var operationId = value.OperationId;
                 pathItem.Operations[OperationType.Put].OperationId = ResolvePutOperationId(operationId);
@@ -67,14 +68,14 @@ public override void Visit(OpenApiOperation operation)
                 throw new ArgumentException($"OperationId is required {PathString}", nameof(operation));
 
             var operationId = operation.OperationId;
-            var operationTypeExtension = operation.Extensions.GetExtension("x-ms-docs-operation-type");
+            var operationTypeExtension = operation.Extensions?.GetExtension("x-ms-docs-operation-type");
             if (operationTypeExtension.IsEquals("function"))
-                operation.Parameters = ResolveFunctionParameters(operation.Parameters);
+                operation.Parameters = ResolveFunctionParameters(operation.Parameters ?? new List<OpenApiParameter>());
 
             // Order matters. Resolve operationId.
             operationId = RemoveHashSuffix(operationId);
             if (operationTypeExtension.IsEquals("action") || operationTypeExtension.IsEquals("function"))
-                operationId = RemoveKeyTypeSegment(operationId, operation.Parameters);
+                operationId = RemoveKeyTypeSegment(operationId, operation.Parameters ?? new List<OpenApiParameter>());
             operationId = SingularizeAndDeduplicateOperationId(operationId.SplitByChar('.'));
             operationId = ResolveODataCastOperationId(operationId);
             operationId = ResolveByRefOperationId(operationId);
diff --git a/src/Microsoft.OpenApi.Hidi/OpenApiService.cs b/src/Microsoft.OpenApi.Hidi/OpenApiService.cs
index d3d3fdd8c..014891a42 100644
--- a/src/Microsoft.OpenApi.Hidi/OpenApiService.cs
+++ b/src/Microsoft.OpenApi.Hidi/OpenApiService.cs
@@ -172,7 +172,7 @@ private static OpenApiDocument ApplyFilters(HidiOptions options, ILogger logger,
                 stopwatch.Start();
                 document = OpenApiFilterService.CreateFilteredDocument(document, predicate);
                 stopwatch.Stop();
-                logger.LogTrace("{Timestamp}ms: Creating filtered OpenApi document with {Paths} paths.", stopwatch.ElapsedMilliseconds, document.Paths.Count);
+                logger.LogTrace("{Timestamp}ms: Creating filtered OpenApi document with {Paths} paths.", stopwatch.ElapsedMilliseconds, document.Paths?.Count);
             }
 
             return document;
@@ -235,7 +235,7 @@ private static async Task<OpenApiDocument> GetOpenApi(HidiOptions options, ILogg
 
                     document = await ConvertCsdlToOpenApi(filteredStream ?? stream, metadataVersion, options.SettingsConfig, cancellationToken).ConfigureAwait(false);
                     stopwatch.Stop();
-                    logger.LogTrace("{Timestamp}ms: Generated OpenAPI with {Paths} paths.", stopwatch.ElapsedMilliseconds, document.Paths.Count);
+                    logger.LogTrace("{Timestamp}ms: Generated OpenAPI with {Paths} paths.", stopwatch.ElapsedMilliseconds, document.Paths?.Count);
                 }
             }
             else if (!string.IsNullOrEmpty(options.OpenApi))
@@ -649,7 +649,7 @@ internal static void WriteTreeDocumentAsMarkdown(string openapiUrl, OpenApiDocum
         {
             var rootNode = OpenApiUrlTreeNode.Create(document, "main");
 
-            writer.WriteLine("# " + document.Info.Title);
+            writer.WriteLine("# " + document.Info?.Title);
             writer.WriteLine();
             writer.WriteLine("API Description: " + openapiUrl);
 
@@ -685,7 +685,7 @@ internal static void WriteTreeDocumentAsHtml(string sourceUrl, OpenApiDocument d
                 </style>
                 <body>
                 """);
-            writer.WriteLine("<h1>" + document.Info.Title + "</h1>");
+            writer.WriteLine("<h1>" + document.Info?.Title + "</h1>");
             writer.WriteLine();
             writer.WriteLine($"<h3> API Description: <a href='{sourceUrl}'>{sourceUrl}</a></h3>");
 
@@ -755,8 +755,8 @@ internal static async Task PluginManifest(HidiOptions options, ILogger logger, C
             // Create OpenAIPluginManifest from ApiDependency and OpenAPI document
             var manifest = new OpenAIPluginManifest
             {
-                NameForHuman = document.Info.Title,
-                DescriptionForHuman = document.Info.Description,
+                NameForHuman = document.Info?.Title,
+                DescriptionForHuman = document.Info?.Description,
                 Api = new()
                 {
                     Type = "openapi",
diff --git a/src/Microsoft.OpenApi/Models/OpenApiComponents.cs b/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
index 52e8cac14..f9828f165 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
@@ -6,6 +6,8 @@
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Writers;
 
+#nullable enable
+
 namespace Microsoft.OpenApi.Models
 {
     /// <summary>
@@ -16,55 +18,55 @@ public class OpenApiComponents : IOpenApiSerializable, IOpenApiExtensible
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiSchema"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiSchema> Schemas { get; set; } = new Dictionary<string, OpenApiSchema>();
+        public IDictionary<string, OpenApiSchema>? Schemas { get; set; } = new Dictionary<string, OpenApiSchema>();
 
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiResponse"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiResponse> Responses { get; set; } = new Dictionary<string, OpenApiResponse>();
+        public IDictionary<string, OpenApiResponse>? Responses { get; set; } = new Dictionary<string, OpenApiResponse>();
 
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiParameter"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiParameter> Parameters { get; set; } =
+        public IDictionary<string, OpenApiParameter>? Parameters { get; set; } =
             new Dictionary<string, OpenApiParameter>();
 
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiExample"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiExample> Examples { get; set; } = new Dictionary<string, OpenApiExample>();
+        public IDictionary<string, OpenApiExample>? Examples { get; set; } = new Dictionary<string, OpenApiExample>();
 
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiRequestBody"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiRequestBody> RequestBodies { get; set; } =
+        public IDictionary<string, OpenApiRequestBody>? RequestBodies { get; set; } =
             new Dictionary<string, OpenApiRequestBody>();
 
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiHeader"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiHeader> Headers { get; set; } = new Dictionary<string, OpenApiHeader>();
+        public IDictionary<string, OpenApiHeader>? Headers { get; set; } = new Dictionary<string, OpenApiHeader>();
 
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiSecurityScheme"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiSecurityScheme> SecuritySchemes { get; set; } =
+        public IDictionary<string, OpenApiSecurityScheme>? SecuritySchemes { get; set; } =
             new Dictionary<string, OpenApiSecurityScheme>();
 
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiLink"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiLink> Links { get; set; } = new Dictionary<string, OpenApiLink>();
+        public IDictionary<string, OpenApiLink>? Links { get; set; } = new Dictionary<string, OpenApiLink>();
 
         /// <summary>
         /// An object to hold reusable <see cref="OpenApiCallback"/> Objects.
         /// </summary>
-        public IDictionary<string, OpenApiCallback> Callbacks { get; set; } = new Dictionary<string, OpenApiCallback>();
+        public IDictionary<string, OpenApiCallback>? Callbacks { get; set; } = new Dictionary<string, OpenApiCallback>();
 
         /// <summary>
         /// This object MAY be extended with Specification Extensions.
         /// </summary>
-        public IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
+        public IDictionary<string, IOpenApiExtension>? Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
         /// <summary>
         /// Parameter-less constructor
@@ -74,7 +76,7 @@ public OpenApiComponents() { }
         /// <summary>
         /// Initializes a copy of an <see cref="OpenApiComponents"/> object
         /// </summary>
-        public OpenApiComponents(OpenApiComponents components)
+        public OpenApiComponents(OpenApiComponents? components)
         {
             Schemas = components?.Schemas != null ? new Dictionary<string, OpenApiSchema>(components.Schemas) : null;
             Responses = components?.Responses != null ? new Dictionary<string, OpenApiResponse>(components.Responses) : null;
diff --git a/src/Microsoft.OpenApi/Models/OpenApiDocument.cs b/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
index 8d4526a20..daf5aee72 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
@@ -12,6 +12,8 @@
 using Microsoft.OpenApi.Services;
 using Microsoft.OpenApi.Writers;
 
+#nullable enable
+
 namespace Microsoft.OpenApi.Models
 {
     /// <summary>
@@ -22,48 +24,48 @@ public class OpenApiDocument : IOpenApiSerializable, IOpenApiExtensible
         /// <summary>
         /// Related workspace containing OpenApiDocuments that are referenced in this document
         /// </summary>
-        public OpenApiWorkspace Workspace { get; set; }
+        public OpenApiWorkspace? Workspace { get; set; }
 
         /// <summary>
         /// REQUIRED. Provides metadata about the API. The metadata MAY be used by tooling as required.
         /// </summary>
-        public OpenApiInfo Info { get; set; }
+        public OpenApiInfo? Info { get; set; }
 
         /// <summary>
         /// An array of Server Objects, which provide connectivity information to a target server.
         /// </summary>
-        public IList<OpenApiServer> Servers { get; set; } = new List<OpenApiServer>();
+        public IList<OpenApiServer>? Servers { get; set; } = new List<OpenApiServer>();
 
         /// <summary>
         /// REQUIRED. The available paths and operations for the API.
         /// </summary>
-        public OpenApiPaths Paths { get; set; }
+        public OpenApiPaths? Paths { get; set; }
 
         /// <summary>
         /// An element to hold various schemas for the specification.
         /// </summary>
-        public OpenApiComponents Components { get; set; }
+        public OpenApiComponents? Components { get; set; }
 
         /// <summary>
         /// A declaration of which security mechanisms can be used across the API.
         /// </summary>
-        public IList<OpenApiSecurityRequirement> SecurityRequirements { get; set; } =
+        public IList<OpenApiSecurityRequirement>? SecurityRequirements { get; set; } =
             new List<OpenApiSecurityRequirement>();
 
         /// <summary>
         /// A list of tags used by the specification with additional metadata.
         /// </summary>
-        public IList<OpenApiTag> Tags { get; set; } = new List<OpenApiTag>();
+        public IList<OpenApiTag>? Tags { get; set; } = new List<OpenApiTag>();
 
         /// <summary>
         /// Additional external documentation.
         /// </summary>
-        public OpenApiExternalDocs ExternalDocs { get; set; }
+        public OpenApiExternalDocs? ExternalDocs { get; set; }
 
         /// <summary>
         /// This object MAY be extended with Specification Extensions.
         /// </summary>
-        public IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
+        public IDictionary<string, IOpenApiExtension>? Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
         /// <summary>
         /// The unique hash code of the generated OpenAPI document
@@ -78,7 +80,7 @@ public OpenApiDocument() {}
         /// <summary>
         /// Initializes a copy of an an <see cref="OpenApiDocument"/> object
         /// </summary>
-        public OpenApiDocument(OpenApiDocument document)
+        public OpenApiDocument(OpenApiDocument? document)
         {
             Workspace = document?.Workspace != null ? new(document?.Workspace) : null;
             Info = document?.Info != null ? new(document?.Info) : null;
@@ -289,7 +291,7 @@ private static string ParseServerUrl(OpenApiServer server)
             return parsedUrl;
         }
 
-        private static void WriteHostInfoV2(IOpenApiWriter writer, IList<OpenApiServer> servers)
+        private static void WriteHostInfoV2(IOpenApiWriter writer, IList<OpenApiServer>? servers)
         {
             if (servers == null || !servers.Any())
             {
@@ -373,7 +375,7 @@ public IEnumerable<OpenApiError> ResolveReferences()
         /// <summary>
         /// Load the referenced <see cref="IOpenApiReferenceable"/> object from a <see cref="OpenApiReference"/> object
         /// </summary>
-        internal T ResolveReferenceTo<T>(OpenApiReference reference) where T : class, IOpenApiReferenceable
+        internal T? ResolveReferenceTo<T>(OpenApiReference reference) where T : class, IOpenApiReferenceable
         {
             if (reference.IsExternal)
             {
@@ -388,7 +390,7 @@ internal T ResolveReferenceTo<T>(OpenApiReference reference) where T : class, IO
         /// <summary>
         /// Load the referenced <see cref="IOpenApiReferenceable"/> object from a <see cref="OpenApiReference"/> object
         /// </summary>
-        public IOpenApiReferenceable ResolveReference(OpenApiReference reference)
+        public IOpenApiReferenceable? ResolveReference(OpenApiReference reference)
         {
             return ResolveReference(reference, false);
         }
@@ -430,7 +432,7 @@ private static string ConvertByteArrayToString(byte[] hash)
         /// <summary>
         /// Load the referenced <see cref="IOpenApiReferenceable"/> object from a <see cref="OpenApiReference"/> object
         /// </summary>
-        internal IOpenApiReferenceable ResolveReference(OpenApiReference reference, bool useExternal)
+        internal IOpenApiReferenceable? ResolveReference(OpenApiReference? reference, bool useExternal)
         {
             if (reference == null)
             {
@@ -455,7 +457,7 @@ internal IOpenApiReferenceable ResolveReference(OpenApiReference reference, bool
             // Special case for Tag
             if (reference.Type == ReferenceType.Tag)
             {
-                foreach (var tag in this.Tags)
+                foreach (var tag in this.Tags ?? Enumerable.Empty<OpenApiTag>())
                 {
                     if (tag.Name == reference.Id)
                     {
@@ -477,34 +479,34 @@ internal IOpenApiReferenceable ResolveReference(OpenApiReference reference, bool
                 switch (reference.Type)
                 {
                     case ReferenceType.Schema:
-                        return this.Components.Schemas[reference.Id];
+                        return this.Components.Schemas?[reference.Id];
 
                     case ReferenceType.Response:
-                        return this.Components.Responses[reference.Id];
+                        return this.Components.Responses?[reference.Id];
 
                     case ReferenceType.Parameter:
-                        return this.Components.Parameters[reference.Id];
+                        return this.Components.Parameters?[reference.Id];
 
                     case ReferenceType.Example:
-                        return this.Components.Examples[reference.Id];
+                        return this.Components.Examples?[reference.Id];
 
                     case ReferenceType.RequestBody:
-                        return this.Components.RequestBodies[reference.Id];
+                        return this.Components.RequestBodies?[reference.Id];
 
                     case ReferenceType.Header:
-                        return this.Components.Headers[reference.Id];
+                        return this.Components.Headers?[reference.Id];
 
                     case ReferenceType.SecurityScheme:
-                        return this.Components.SecuritySchemes[reference.Id];
+                        return this.Components.SecuritySchemes?[reference.Id];
 
                     case ReferenceType.Link:
-                        return this.Components.Links[reference.Id];
+                        return this.Components.Links?[reference.Id];
 
                     case ReferenceType.Callback:
-                        return this.Components.Callbacks[reference.Id];
+                        return this.Components.Callbacks?[reference.Id];
 
                     case ReferenceType.Path:
-                        return this.Paths[reference.Id];
+                        return this.Paths?[reference.Id];
 
                     default:
                         throw new OpenApiException(Properties.SRResource.InvalidReferenceType);
@@ -519,9 +521,9 @@ internal IOpenApiReferenceable ResolveReference(OpenApiReference reference, bool
 
     internal class FindSchemaReferences : OpenApiVisitorBase
     {
-        private Dictionary<string, OpenApiSchema> Schemas;
+        private Dictionary<string, OpenApiSchema> Schemas = new Dictionary<string, OpenApiSchema>();
 
-        public static void ResolveSchemas(OpenApiComponents components, Dictionary<string, OpenApiSchema> schemas )
+        public static void ResolveSchemas(OpenApiComponents? components, Dictionary<string, OpenApiSchema> schemas )
         {
             var visitor = new FindSchemaReferences();
             visitor.Schemas = schemas;
diff --git a/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs b/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
index 444f41ba5..5d0b11a1f 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
@@ -6,6 +6,8 @@
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Writers;
 
+#nullable enable
+
 namespace Microsoft.OpenApi.Models
 {
     /// <summary>
@@ -16,19 +18,19 @@ public class OpenApiMediaType : IOpenApiSerializable, IOpenApiExtensible
         /// <summary>
         /// The schema defining the type used for the request body.
         /// </summary>
-        public OpenApiSchema Schema { get; set; }
+        public OpenApiSchema? Schema { get; set; }
 
         /// <summary>
         /// Example of the media type.
         /// The example object SHOULD be in the correct format as specified by the media type.
         /// </summary>
-        public IOpenApiAny Example { get; set; }
+        public IOpenApiAny? Example { get; set; }
 
         /// <summary>
         /// Examples of the media type.
         /// Each example object SHOULD match the media type and specified schema if present.
         /// </summary>
-        public IDictionary<string, OpenApiExample> Examples { get; set; } = new Dictionary<string, OpenApiExample>();
+        public IDictionary<string, OpenApiExample>? Examples { get; set; } = new Dictionary<string, OpenApiExample>();
 
         /// <summary>
         /// A map between a property name and its encoding information.
@@ -36,12 +38,12 @@ public class OpenApiMediaType : IOpenApiSerializable, IOpenApiExtensible
         /// The encoding object SHALL only apply to requestBody objects
         /// when the media type is multipart or application/x-www-form-urlencoded.
         /// </summary>
-        public IDictionary<string, OpenApiEncoding> Encoding { get; set; } = new Dictionary<string, OpenApiEncoding>();
+        public IDictionary<string, OpenApiEncoding>? Encoding { get; set; } = new Dictionary<string, OpenApiEncoding>();
 
         /// <summary>
         /// Serialize <see cref="OpenApiExternalDocs"/> to Open Api v3.0.
         /// </summary>
-        public IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
+        public IDictionary<string, IOpenApiExtension>? Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
         /// <summary>
         /// Parameterless constructor
@@ -51,7 +53,7 @@ public OpenApiMediaType() {}
         /// <summary>
         /// Initializes a copy of an <see cref="OpenApiMediaType"/> object
         /// </summary>
-        public OpenApiMediaType(OpenApiMediaType mediaType)
+        public OpenApiMediaType(OpenApiMediaType? mediaType)
         {
             Schema = mediaType?.Schema != null ? new(mediaType?.Schema) : null;
             Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(mediaType?.Example);
diff --git a/src/Microsoft.OpenApi/Models/OpenApiOperation.cs b/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
index 360cfe7c1..4765e929d 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
@@ -7,6 +7,8 @@
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Writers;
 
+#nullable enable
+
 namespace Microsoft.OpenApi.Models
 {
     /// <summary>
@@ -23,30 +25,30 @@ public class OpenApiOperation : IOpenApiSerializable, IOpenApiExtensible
         /// A list of tags for API documentation control.
         /// Tags can be used for logical grouping of operations by resources or any other qualifier.
         /// </summary>
-        public IList<OpenApiTag> Tags { get; set; } = new List<OpenApiTag>();
+        public IList<OpenApiTag>? Tags { get; set; } = new List<OpenApiTag>();
 
         /// <summary>
         /// A short summary of what the operation does.
         /// </summary>
-        public string Summary { get; set; }
+        public string? Summary { get; set; }
 
         /// <summary>
         /// A verbose explanation of the operation behavior.
         /// CommonMark syntax MAY be used for rich text representation.
         /// </summary>
-        public string Description { get; set; }
+        public string? Description { get; set; }
 
         /// <summary>
         /// Additional external documentation for this operation.
         /// </summary>
-        public OpenApiExternalDocs ExternalDocs { get; set; }
+        public OpenApiExternalDocs? ExternalDocs { get; set; }
 
         /// <summary>
         /// Unique string used to identify the operation. The id MUST be unique among all operations described in the API.
         /// Tools and libraries MAY use the operationId to uniquely identify an operation, therefore,
         /// it is RECOMMENDED to follow common programming naming conventions.
         /// </summary>
-        public string OperationId { get; set; }
+        public string? OperationId { get; set; }
 
         /// <summary>
         /// A list of parameters that are applicable for this operation.
@@ -54,7 +56,7 @@ public class OpenApiOperation : IOpenApiSerializable, IOpenApiExtensible
         /// The list MUST NOT include duplicated parameters. A unique parameter is defined by a combination of a name and location.
         /// The list can use the Reference Object to link to parameters that are defined at the OpenAPI Object's components/parameters.
         /// </summary>
-        public IList<OpenApiParameter> Parameters { get; set; } = new List<OpenApiParameter>();
+        public IList<OpenApiParameter>? Parameters { get; set; } = new List<OpenApiParameter>();
 
         /// <summary>
         /// The request body applicable for this operation.
@@ -62,12 +64,12 @@ public class OpenApiOperation : IOpenApiSerializable, IOpenApiExtensible
         /// has explicitly defined semantics for request bodies.
         /// In other cases where the HTTP spec is vague, requestBody SHALL be ignored by consumers.
         /// </summary>
-        public OpenApiRequestBody RequestBody { get; set; }
+        public OpenApiRequestBody? RequestBody { get; set; }
 
         /// <summary>
         /// REQUIRED. The list of possible responses as they are returned from executing this operation.
         /// </summary>
-        public OpenApiResponses Responses { get; set; } = new();
+        public OpenApiResponses? Responses { get; set; } = new();
 
         /// <summary>
         /// A map of possible out-of band callbacks related to the parent operation.
@@ -77,7 +79,7 @@ public class OpenApiOperation : IOpenApiSerializable, IOpenApiExtensible
         /// The key value used to identify the callback object is an expression, evaluated at runtime,
         /// that identifies a URL to use for the callback operation.
         /// </summary>
-        public IDictionary<string, OpenApiCallback> Callbacks { get; set; } = new Dictionary<string, OpenApiCallback>();
+        public IDictionary<string, OpenApiCallback>? Callbacks { get; set; } = new Dictionary<string, OpenApiCallback>();
 
         /// <summary>
         /// Declares this operation to be deprecated. Consumers SHOULD refrain from usage of the declared operation.
@@ -91,19 +93,19 @@ public class OpenApiOperation : IOpenApiSerializable, IOpenApiExtensible
         /// This definition overrides any declared top-level security.
         /// To remove a top-level security declaration, an empty array can be used.
         /// </summary>
-        public IList<OpenApiSecurityRequirement> Security { get; set; } = new List<OpenApiSecurityRequirement>();
+        public IList<OpenApiSecurityRequirement>? Security { get; set; } = new List<OpenApiSecurityRequirement>();
 
         /// <summary>
         /// An alternative server array to service this operation.
         /// If an alternative server object is specified at the Path Item Object or Root level,
         /// it will be overridden by this value.
         /// </summary>
-        public IList<OpenApiServer> Servers { get; set; } = new List<OpenApiServer>();
+        public IList<OpenApiServer>? Servers { get; set; } = new List<OpenApiServer>();
 
         /// <summary>
         /// This object MAY be extended with Specification Extensions.
         /// </summary>
-        public IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
+        public IDictionary<string, IOpenApiExtension>? Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
         /// <summary>
         /// Parameterless constructor
@@ -113,9 +115,9 @@ public OpenApiOperation() {}
         /// <summary>
         /// Initializes a copy of an <see cref="OpenApiOperation"/> object
         /// </summary>
-        public OpenApiOperation(OpenApiOperation operation)
+        public OpenApiOperation(OpenApiOperation? operation)
         {
-            Tags = operation?.Tags != null ? new List<OpenApiTag>(operation?.Tags) : null;
+            Tags = operation?.Tags != null ? new List<OpenApiTag>(operation.Tags) : null;
             Summary = operation?.Summary ?? Summary;
             Description = operation?.Description ?? Description;
             ExternalDocs = operation?.ExternalDocs != null ? new(operation?.ExternalDocs) : null;
diff --git a/src/Microsoft.OpenApi/Services/OpenApiWalker.cs b/src/Microsoft.OpenApi/Services/OpenApiWalker.cs
index 446663f6b..6a328d68f 100644
--- a/src/Microsoft.OpenApi/Services/OpenApiWalker.cs
+++ b/src/Microsoft.OpenApi/Services/OpenApiWalker.cs
@@ -87,11 +87,11 @@ internal void Walk(OpenApiExternalDocs externalDocs)
 
             _visitor.Visit(externalDocs);
         }
-
+#nullable enable
         /// <summary>
         /// Visits <see cref="OpenApiComponents"/> and child objects
         /// </summary>
-        internal void Walk(OpenApiComponents components)
+        internal void Walk(OpenApiComponents? components)
         {
             if (components == null)
             {
@@ -207,6 +207,8 @@ internal void Walk(OpenApiComponents components)
             Walk(components as IOpenApiExtensible);
         }
 
+#nullable restore
+        
         /// <summary>
         /// Visits <see cref="OpenApiPaths"/> and child objects
         /// </summary>
diff --git a/src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs b/src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs
index 7b85dd680..616b156e1 100644
--- a/src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs
+++ b/src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs
@@ -125,6 +125,7 @@ public static void WriteProperty<T>(this IOpenApiWriter writer, string name, T v
             writer.WriteValue(value);
         }
 
+#nullable enable
         /// <summary>
         /// Write the optional Open API object/element.
         /// </summary>
@@ -136,7 +137,7 @@ public static void WriteProperty<T>(this IOpenApiWriter writer, string name, T v
         public static void WriteOptionalObject<T>(
             this IOpenApiWriter writer,
             string name,
-            T value,
+            T? value,
             Action<IOpenApiWriter, T> action)
             where T : IOpenApiElement
         {
@@ -162,7 +163,7 @@ public static void WriteOptionalObject<T>(
         public static void WriteRequiredObject<T>(
             this IOpenApiWriter writer,
             string name,
-            T value,
+            T? value,
             Action<IOpenApiWriter, T> action)
             where T : IOpenApiElement
         {
@@ -180,6 +181,7 @@ public static void WriteRequiredObject<T>(
             }
         }
 
+#nullable restore
         /// <summary>
         /// Write the optional of collection string.
         /// </summary>
diff --git a/test/Microsoft.OpenApi.Hidi.Tests/Formatters/PowerShellFormatterTests.cs b/test/Microsoft.OpenApi.Hidi.Tests/Formatters/PowerShellFormatterTests.cs
index a5bf74219..f375f2cc3 100644
--- a/test/Microsoft.OpenApi.Hidi.Tests/Formatters/PowerShellFormatterTests.cs
+++ b/test/Microsoft.OpenApi.Hidi.Tests/Formatters/PowerShellFormatterTests.cs
@@ -57,19 +57,19 @@ public void RemoveAnyOfAndOneOfFromSchema()
             var walker = new OpenApiWalker(powerShellFormatter);
             walker.Walk(openApiDocument);
 
-            var testSchema = openApiDocument.Components.Schemas["TestSchema"];
-            var averageAudioDegradationProperty = testSchema.Properties["averageAudioDegradation"];
-            var defaultPriceProperty = testSchema.Properties["defaultPrice"];
+            var testSchema = openApiDocument.Components?.Schemas?["TestSchema"];
+            var averageAudioDegradationProperty = testSchema?.Properties["averageAudioDegradation"];
+            var defaultPriceProperty = testSchema?.Properties["defaultPrice"];
 
             // Assert
-            Assert.Null(averageAudioDegradationProperty.AnyOf);
-            Assert.Equal("number", averageAudioDegradationProperty.Type);
-            Assert.Equal("float", averageAudioDegradationProperty.Format);
-            Assert.True(averageAudioDegradationProperty.Nullable);
-            Assert.Null(defaultPriceProperty.OneOf);
-            Assert.Equal("number", defaultPriceProperty.Type);
-            Assert.Equal("double", defaultPriceProperty.Format);
-            Assert.NotNull(testSchema.AdditionalProperties);
+            Assert.Null(averageAudioDegradationProperty?.AnyOf);
+            Assert.Equal("number", averageAudioDegradationProperty?.Type);
+            Assert.Equal("float", averageAudioDegradationProperty?.Format);
+            Assert.True(averageAudioDegradationProperty?.Nullable);
+            Assert.Null(defaultPriceProperty?.OneOf);
+            Assert.Equal("number", defaultPriceProperty?.Type);
+            Assert.Equal("double", defaultPriceProperty?.Format);
+            Assert.NotNull(testSchema?.AdditionalProperties);
         }
 
         [Fact]
@@ -83,7 +83,7 @@ public void ResolveFunctionParameters()
             var walker = new OpenApiWalker(powerShellFormatter);
             walker.Walk(openApiDocument);
 
-            var idsParameter = openApiDocument.Paths["/foo"].Operations[OperationType.Get].Parameters.Where(static p => p.Name == "ids").FirstOrDefault();
+            var idsParameter = openApiDocument.Paths?["/foo"].Operations[OperationType.Get].Parameters?.Where(static p => p.Name == "ids").FirstOrDefault();
 
             // Assert
             Assert.Null(idsParameter?.Content);
diff --git a/test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiFilterServiceTests.cs b/test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiFilterServiceTests.cs
index 5fb1b15f9..02e6cedb0 100644
--- a/test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiFilterServiceTests.cs
+++ b/test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiFilterServiceTests.cs
@@ -43,6 +43,7 @@ public void ReturnFilteredOpenApiDocumentBasedOnOperationIdsAndTags(string? oper
 
             // Assert
             Assert.NotNull(subsetOpenApiDocument);
+            Assert.NotNull(subsetOpenApiDocument.Paths);
             Assert.NotEmpty(subsetOpenApiDocument.Paths);
             Assert.Equal(expectedPathCount, subsetOpenApiDocument.Paths.Count);
         }
@@ -62,6 +63,7 @@ public void ReturnFilteredOpenApiDocumentBasedOnPostmanCollection()
 
             // Assert
             Assert.NotNull(subsetOpenApiDocument);
+            Assert.NotNull(subsetOpenApiDocument.Paths);
             Assert.NotEmpty(subsetOpenApiDocument.Paths);
             Assert.Equal(3, subsetOpenApiDocument.Paths.Count);
         }
@@ -150,10 +152,11 @@ public void ContinueProcessingWhenUrlsInCollectionAreMissingFromSourceDocument()
             var pathCount = requestUrls.Count;
             var predicate = OpenApiFilterService.CreatePredicate(requestUrls: requestUrls, source: _openApiDocumentMock);
             var subsetOpenApiDocument = OpenApiFilterService.CreateFilteredDocument(_openApiDocumentMock, predicate);
-            var subsetPathCount = subsetOpenApiDocument.Paths.Count;
+            var subsetPathCount = subsetOpenApiDocument.Paths?.Count;
 
             // Assert
             Assert.NotNull(subsetOpenApiDocument);
+            Assert.NotNull(subsetOpenApiDocument.Paths);
             Assert.NotEmpty(subsetOpenApiDocument.Paths);
             Assert.Equal(2, subsetPathCount);
             Assert.NotEqual(pathCount, subsetPathCount);
@@ -180,6 +183,7 @@ public void ReturnsPathParametersOnSlicingBasedOnOperationIdsOrTags(string? oper
             var subsetOpenApiDocument = OpenApiFilterService.CreateFilteredDocument(_openApiDocumentMock, predicate);
 
             // Assert
+            Assert.NotNull(subsetOpenApiDocument.Paths);
             foreach (var pathItem in subsetOpenApiDocument.Paths)
             {
                 Assert.True(pathItem.Value.Parameters.Any());
diff --git a/test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiServiceTests.cs b/test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiServiceTests.cs
index 7314da8ab..544aa7df1 100644
--- a/test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiServiceTests.cs
+++ b/test/Microsoft.OpenApi.Hidi.Tests/Services/OpenApiServiceTests.cs
@@ -39,6 +39,7 @@ public async Task ReturnConvertedCSDLFile()
 
             // Assert
             Assert.NotNull(openApiDoc);
+            Assert.NotNull(openApiDoc.Paths);
             Assert.NotEmpty(openApiDoc.Paths);
             Assert.Equal(expectedPathCount, openApiDoc.Paths.Count);
         }
@@ -61,6 +62,7 @@ public async Task ReturnFilteredOpenApiDocBasedOnOperationIdsAndInputCsdlDocumen
 
             // Assert
             Assert.NotNull(subsetOpenApiDocument);
+            Assert.NotNull(subsetOpenApiDocument.Paths);
             Assert.NotEmpty(subsetOpenApiDocument.Paths);
             Assert.Equal(expectedPathCount, subsetOpenApiDocument.Paths.Count);
         }
diff --git a/test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt b/test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt
index 37f40bb11..d0d179ebb 100755
--- a/test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt
+++ b/test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt
@@ -426,17 +426,17 @@ namespace Microsoft.OpenApi.Models
     public class OpenApiComponents : Microsoft.OpenApi.Interfaces.IOpenApiElement, Microsoft.OpenApi.Interfaces.IOpenApiExtensible, Microsoft.OpenApi.Interfaces.IOpenApiSerializable
     {
         public OpenApiComponents() { }
-        public OpenApiComponents(Microsoft.OpenApi.Models.OpenApiComponents components) { }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiCallback> Callbacks { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiExample> Examples { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Interfaces.IOpenApiExtension> Extensions { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiHeader> Headers { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiLink> Links { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiParameter> Parameters { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiRequestBody> RequestBodies { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiResponse> Responses { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiSchema> Schemas { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiSecurityScheme> SecuritySchemes { get; set; }
+        public OpenApiComponents(Microsoft.OpenApi.Models.OpenApiComponents? components) { }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiCallback>? Callbacks { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiExample>? Examples { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Interfaces.IOpenApiExtension>? Extensions { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiHeader>? Headers { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiLink>? Links { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiParameter>? Parameters { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiRequestBody>? RequestBodies { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiResponse>? Responses { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiSchema>? Schemas { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiSecurityScheme>? SecuritySchemes { get; set; }
         public void SerializeAsV2(Microsoft.OpenApi.Writers.IOpenApiWriter writer) { }
         public void SerializeAsV3(Microsoft.OpenApi.Writers.IOpenApiWriter writer) { }
     }
@@ -592,18 +592,18 @@ namespace Microsoft.OpenApi.Models
     public class OpenApiDocument : Microsoft.OpenApi.Interfaces.IOpenApiElement, Microsoft.OpenApi.Interfaces.IOpenApiExtensible, Microsoft.OpenApi.Interfaces.IOpenApiSerializable
     {
         public OpenApiDocument() { }
-        public OpenApiDocument(Microsoft.OpenApi.Models.OpenApiDocument document) { }
-        public Microsoft.OpenApi.Models.OpenApiComponents Components { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Interfaces.IOpenApiExtension> Extensions { get; set; }
-        public Microsoft.OpenApi.Models.OpenApiExternalDocs ExternalDocs { get; set; }
+        public OpenApiDocument(Microsoft.OpenApi.Models.OpenApiDocument? document) { }
+        public Microsoft.OpenApi.Models.OpenApiComponents? Components { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Interfaces.IOpenApiExtension>? Extensions { get; set; }
+        public Microsoft.OpenApi.Models.OpenApiExternalDocs? ExternalDocs { get; set; }
         public string HashCode { get; }
-        public Microsoft.OpenApi.Models.OpenApiInfo Info { get; set; }
-        public Microsoft.OpenApi.Models.OpenApiPaths Paths { get; set; }
-        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiSecurityRequirement> SecurityRequirements { get; set; }
-        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiServer> Servers { get; set; }
-        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiTag> Tags { get; set; }
-        public Microsoft.OpenApi.Services.OpenApiWorkspace Workspace { get; set; }
-        public Microsoft.OpenApi.Interfaces.IOpenApiReferenceable ResolveReference(Microsoft.OpenApi.Models.OpenApiReference reference) { }
+        public Microsoft.OpenApi.Models.OpenApiInfo? Info { get; set; }
+        public Microsoft.OpenApi.Models.OpenApiPaths? Paths { get; set; }
+        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiSecurityRequirement>? SecurityRequirements { get; set; }
+        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiServer>? Servers { get; set; }
+        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiTag>? Tags { get; set; }
+        public Microsoft.OpenApi.Services.OpenApiWorkspace? Workspace { get; set; }
+        public Microsoft.OpenApi.Interfaces.IOpenApiReferenceable? ResolveReference(Microsoft.OpenApi.Models.OpenApiReference reference) { }
         public System.Collections.Generic.IEnumerable<Microsoft.OpenApi.Models.OpenApiError> ResolveReferences() { }
         public void SerializeAsV2(Microsoft.OpenApi.Writers.IOpenApiWriter writer) { }
         public void SerializeAsV3(Microsoft.OpenApi.Writers.IOpenApiWriter writer) { }
@@ -738,12 +738,12 @@ namespace Microsoft.OpenApi.Models
     public class OpenApiMediaType : Microsoft.OpenApi.Interfaces.IOpenApiElement, Microsoft.OpenApi.Interfaces.IOpenApiExtensible, Microsoft.OpenApi.Interfaces.IOpenApiSerializable
     {
         public OpenApiMediaType() { }
-        public OpenApiMediaType(Microsoft.OpenApi.Models.OpenApiMediaType mediaType) { }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiEncoding> Encoding { get; set; }
-        public Microsoft.OpenApi.Any.IOpenApiAny Example { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiExample> Examples { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Interfaces.IOpenApiExtension> Extensions { get; set; }
-        public Microsoft.OpenApi.Models.OpenApiSchema Schema { get; set; }
+        public OpenApiMediaType(Microsoft.OpenApi.Models.OpenApiMediaType? mediaType) { }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiEncoding>? Encoding { get; set; }
+        public Microsoft.OpenApi.Any.IOpenApiAny? Example { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiExample>? Examples { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Interfaces.IOpenApiExtension>? Extensions { get; set; }
+        public Microsoft.OpenApi.Models.OpenApiSchema? Schema { get; set; }
         public void SerializeAsV2(Microsoft.OpenApi.Writers.IOpenApiWriter writer) { }
         public void SerializeAsV3(Microsoft.OpenApi.Writers.IOpenApiWriter writer) { }
     }
@@ -775,20 +775,20 @@ namespace Microsoft.OpenApi.Models
     {
         public const bool DeprecatedDefault = false;
         public OpenApiOperation() { }
-        public OpenApiOperation(Microsoft.OpenApi.Models.OpenApiOperation operation) { }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiCallback> Callbacks { get; set; }
+        public OpenApiOperation(Microsoft.OpenApi.Models.OpenApiOperation? operation) { }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Models.OpenApiCallback>? Callbacks { get; set; }
         public bool Deprecated { get; set; }
-        public string Description { get; set; }
-        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Interfaces.IOpenApiExtension> Extensions { get; set; }
-        public Microsoft.OpenApi.Models.OpenApiExternalDocs ExternalDocs { get; set; }
-        public string OperationId { get; set; }
-        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiParameter> Parameters { get; set; }
-        public Microsoft.OpenApi.Models.OpenApiRequestBody RequestBody { get; set; }
-        public Microsoft.OpenApi.Models.OpenApiResponses Responses { get; set; }
-        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiSecurityRequirement> Security { get; set; }
-        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiServer> Servers { get; set; }
-        public string Summary { get; set; }
-        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiTag> Tags { get; set; }
+        public string? Description { get; set; }
+        public System.Collections.Generic.IDictionary<string, Microsoft.OpenApi.Interfaces.IOpenApiExtension>? Extensions { get; set; }
+        public Microsoft.OpenApi.Models.OpenApiExternalDocs? ExternalDocs { get; set; }
+        public string? OperationId { get; set; }
+        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiParameter>? Parameters { get; set; }
+        public Microsoft.OpenApi.Models.OpenApiRequestBody? RequestBody { get; set; }
+        public Microsoft.OpenApi.Models.OpenApiResponses? Responses { get; set; }
+        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiSecurityRequirement>? Security { get; set; }
+        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiServer>? Servers { get; set; }
+        public string? Summary { get; set; }
+        public System.Collections.Generic.IList<Microsoft.OpenApi.Models.OpenApiTag>? Tags { get; set; }
         public void SerializeAsV2(Microsoft.OpenApi.Writers.IOpenApiWriter writer) { }
         public void SerializeAsV3(Microsoft.OpenApi.Writers.IOpenApiWriter writer) { }
     }
@@ -1575,7 +1575,7 @@ namespace Microsoft.OpenApi.Writers
             where T : Microsoft.OpenApi.Interfaces.IOpenApiElement { }
         public static void WriteOptionalMap<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, System.Collections.Generic.IDictionary<string, T> elements, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, string, T> action)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiElement { }
-        public static void WriteOptionalObject<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, T value, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, T> action)
+        public static void WriteOptionalObject<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, T? value, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, T> action)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiElement { }
         public static void WriteProperty(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, string value) { }
         public static void WriteProperty(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, bool value, bool defaultValue = false) { }
@@ -1589,7 +1589,7 @@ namespace Microsoft.OpenApi.Writers
         public static void WriteRequiredMap(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, System.Collections.Generic.IDictionary<string, string> elements, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, string> action) { }
         public static void WriteRequiredMap<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, System.Collections.Generic.IDictionary<string, T> elements, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, T> action)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiElement { }
-        public static void WriteRequiredObject<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, T value, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, T> action)
+        public static void WriteRequiredObject<T>(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, T? value, System.Action<Microsoft.OpenApi.Writers.IOpenApiWriter, T> action)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiElement { }
         public static void WriteRequiredProperty(this Microsoft.OpenApi.Writers.IOpenApiWriter writer, string name, string value) { }
     }