diff --git a/src/Microsoft.OpenApi/Models/OpenApiCallback.cs b/src/Microsoft.OpenApi/Models/OpenApiCallback.cs
index e9701b17c..2dcae12d1 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiCallback.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiCallback.cs
@@ -45,10 +45,10 @@ public OpenApiCallback() { }
         /// </summary>
         public OpenApiCallback(OpenApiCallback callback)
         {
-            PathItems = new(callback.PathItems);
-            UnresolvedReference = callback.UnresolvedReference;
-            Reference = new(callback.Reference);
-            Extensions = new Dictionary<string, IOpenApiExtension>(callback.Extensions);
+            PathItems = callback?.PathItems != null ? new(callback?.PathItems) : null;
+            UnresolvedReference = callback?.UnresolvedReference ?? UnresolvedReference;
+            Reference = callback?.Reference != null ? new(callback?.Reference) : null;
+            Extensions = callback?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(callback.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiComponents.cs b/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
index c23e569c5..1f41080bc 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
@@ -78,16 +78,16 @@ public OpenApiComponents() { }
         /// </summary>
         public OpenApiComponents(OpenApiComponents components)
         {
-            Schemas = new Dictionary<string, OpenApiSchema>(components.Schemas);
-            Responses = new Dictionary<string, OpenApiResponse>(components.Responses);
-            Parameters = new Dictionary<string, OpenApiParameter>(components.Parameters);
-            Examples = new Dictionary<string, OpenApiExample>(components.Examples);
-            RequestBodies = new Dictionary<string, OpenApiRequestBody>(components.RequestBodies);
-            Headers = new Dictionary<string, OpenApiHeader>(components.Headers);
-            SecuritySchemes = new Dictionary<string, OpenApiSecurityScheme>(components.SecuritySchemes);
-            Links = new Dictionary<string, OpenApiLink>(components.Links);
-            Callbacks = new Dictionary<string, OpenApiCallback>(components.Callbacks);
-            Extensions = new Dictionary<string, IOpenApiExtension>(components.Extensions);
+            Schemas = components?.Schemas != null ? new Dictionary<string, OpenApiSchema>(components.Schemas) : null;
+            Responses = components?.Responses != null ? new Dictionary<string, OpenApiResponse>(components.Responses) : null;
+            Parameters = components?.Parameters != null ? new Dictionary<string, OpenApiParameter>(components.Parameters) : null;
+            Examples = components?.Examples != null ? new Dictionary<string, OpenApiExample>(components.Examples) : null;
+            RequestBodies = components?.RequestBodies != null ? new Dictionary<string, OpenApiRequestBody>(components.RequestBodies) : null;
+            Headers = components?.Headers != null ? new Dictionary<string, OpenApiHeader>(components.Headers) : null;
+            SecuritySchemes = components?.SecuritySchemes != null ? new Dictionary<string, OpenApiSecurityScheme>(components.SecuritySchemes) : null;
+            Links = components?.Links != null ? new Dictionary<string, OpenApiLink>(components.Links) : null;
+            Callbacks = components?.Callbacks != null ? new Dictionary<string, OpenApiCallback>(components.Callbacks) : null;
+            Extensions = components?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(components.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiContact.cs b/src/Microsoft.OpenApi/Models/OpenApiContact.cs
index 9447d424e..352697bf2 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiContact.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiContact.cs
@@ -45,10 +45,10 @@ public OpenApiContact() { }
         /// </summary>
         public OpenApiContact(OpenApiContact contact)
         {
-            Name = contact.Name;
-            Url = new Uri(contact.Url.OriginalString);
-            Email = contact.Email;
-            Extensions = new Dictionary<string, IOpenApiExtension>(contact.Extensions);
+            Name = contact?.Name ?? Name;
+            Url = contact?.Url != null ? new Uri(contact.Url.OriginalString) : null;
+            Email = contact?.Email ?? Email;
+            Extensions = contact?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(contact.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiDiscriminator.cs b/src/Microsoft.OpenApi/Models/OpenApiDiscriminator.cs
index e03c7d59a..9ae7f0e6a 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiDiscriminator.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiDiscriminator.cs
@@ -32,8 +32,8 @@ public OpenApiDiscriminator() { }
         /// </summary>
         public OpenApiDiscriminator(OpenApiDiscriminator discriminator)
         {
-            PropertyName = discriminator.PropertyName;
-            Mapping = new Dictionary<string, string>(discriminator.Mapping);
+            PropertyName = discriminator?.PropertyName ?? PropertyName;
+            Mapping = discriminator?.Mapping != null ? new Dictionary<string, string>(discriminator.Mapping) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiDocument.cs b/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
index 44cbc71ab..01edcebba 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
@@ -72,15 +72,15 @@ public OpenApiDocument() {}
         /// </summary>
         public OpenApiDocument(OpenApiDocument document)
         {
-            Workspace = new(document.Workspace);
-            Info = new(document.Info);
-            Servers = new List<OpenApiServer>(document.Servers);
-            Paths = new(document.Paths);
-            Components = new(document.Components);
-            SecurityRequirements = new List<OpenApiSecurityRequirement>(document.SecurityRequirements);
-            Tags = new List<OpenApiTag>(document.Tags);
-            ExternalDocs = new(document.ExternalDocs);
-            Extensions = new Dictionary<string, IOpenApiExtension>(document.Extensions);
+            Workspace = document?.Workspace != null ? new(document?.Workspace) : null;
+            Info = document?.Info != null ? new(document?.Info) : null;
+            Servers = document?.Servers != null ? new List<OpenApiServer>(document.Servers) : null;
+            Paths = document?.Paths != null ? new(document?.Paths) : null;
+            Components = document?.Components != null ? new(document?.Components) : null;
+            SecurityRequirements = document?.SecurityRequirements != null ? new List<OpenApiSecurityRequirement>(document.SecurityRequirements) : null;
+            Tags = document?.Tags != null ? new List<OpenApiTag>(document.Tags) : null;
+            ExternalDocs = document?.ExternalDocs != null ? new(document?.ExternalDocs) : null;
+            Extensions = document?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(document.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiEncoding.cs b/src/Microsoft.OpenApi/Models/OpenApiEncoding.cs
index 533cb7e80..ddb4162bc 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiEncoding.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiEncoding.cs
@@ -63,12 +63,12 @@ public OpenApiEncoding() {}
         /// </summary>
         public OpenApiEncoding(OpenApiEncoding encoding)
         {
-            ContentType = encoding.ContentType;
-            Headers = new Dictionary<string, OpenApiHeader>(encoding.Headers);
-            Style = encoding.Style;
-            Explode = encoding.Explode;
-            AllowReserved = encoding.AllowReserved;
-            Extensions = new Dictionary<string, IOpenApiExtension>(encoding.Extensions);
+            ContentType = encoding?.ContentType ?? ContentType;
+            Headers = encoding?.Headers != null ? new Dictionary<string, OpenApiHeader>(encoding.Headers) : null;
+            Style = encoding?.Style ?? Style;
+            Explode = encoding?.Explode ?? Explode;
+            AllowReserved = encoding?.AllowReserved ?? AllowReserved;
+            Extensions = encoding?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(encoding.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiExample.cs b/src/Microsoft.OpenApi/Models/OpenApiExample.cs
index 5e105be26..4d091a361 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiExample.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiExample.cs
@@ -64,13 +64,13 @@ public OpenApiExample() {}
         /// </summary>
         public OpenApiExample(OpenApiExample example)
         {
-            Summary = example.Summary;
-            Description = example.Description;
-            Value = OpenApiAnyCloneHelper.CloneFromCopyConstructor(example.Value);
-            ExternalValue = example.ExternalValue;
-            Extensions = new Dictionary<string, IOpenApiExtension>(example.Extensions);
-            Reference = new(example.Reference);
-            UnresolvedReference = example.UnresolvedReference;
+            Summary = example?.Summary ?? Summary;
+            Description = example?.Description ?? Description;
+            Value = OpenApiAnyCloneHelper.CloneFromCopyConstructor(example?.Value);
+            ExternalValue = example?.ExternalValue ?? ExternalValue;
+            Extensions = example?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(example.Extensions) : null;
+            Reference = example?.Reference != null ? new(example?.Reference) : null;
+            UnresolvedReference = example?.UnresolvedReference ?? UnresolvedReference;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiExternalDocs.cs b/src/Microsoft.OpenApi/Models/OpenApiExternalDocs.cs
index 95af8f01b..9ad3b9e55 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiExternalDocs.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiExternalDocs.cs
@@ -39,9 +39,9 @@ public OpenApiExternalDocs() {}
         /// </summary>
         public OpenApiExternalDocs(OpenApiExternalDocs externalDocs)
         {
-            Description = externalDocs.Description;
-            Url = new Uri(externalDocs.Url.OriginalString);
-            Extensions = new Dictionary<string, IOpenApiExtension>(externalDocs.Extensions);
+            Description = externalDocs?.Description ?? Description;
+            Url = externalDocs?.Url != null ? new Uri(externalDocs.Url.OriginalString) : null;
+            Extensions = externalDocs?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(externalDocs.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiHeader.cs b/src/Microsoft.OpenApi/Models/OpenApiHeader.cs
index b91440df8..fb4411478 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiHeader.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiHeader.cs
@@ -96,20 +96,20 @@ public OpenApiHeader() {}
         /// </summary>
         public OpenApiHeader(OpenApiHeader header)
         {
-            UnresolvedReference = header.UnresolvedReference;
-            Reference = new(header.Reference);
-            Description = header.Description;
-            Required = header.Required;
-            Deprecated = header.Deprecated;
-            AllowEmptyValue = header.AllowEmptyValue;
-            Style = header.Style;
-            Explode = header.Explode;
-            AllowReserved = header.AllowReserved;
-            Schema = new(header.Schema);
-            Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(header.Example);
-            Examples = new Dictionary<string, OpenApiExample>(header.Examples);
-            Content = new Dictionary<string, OpenApiMediaType>(header.Content);
-            Extensions = new Dictionary<string, IOpenApiExtension>(header.Extensions);
+            UnresolvedReference = header?.UnresolvedReference ?? UnresolvedReference;
+            Reference = header?.Reference != null ? new(header?.Reference) : null;
+            Description = header?.Description ?? Description;
+            Required = header?.Required ?? Required;
+            Deprecated = header?.Deprecated ?? Deprecated;
+            AllowEmptyValue = header?.AllowEmptyValue ?? AllowEmptyValue;
+            Style = header?.Style ?? Style;
+            Explode = header?.Explode ?? Explode;
+            AllowReserved = header?.AllowReserved ?? AllowReserved;
+            Schema = header?.Schema != null ? new(header?.Schema) : null;
+            Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(header?.Example);
+            Examples = header?.Examples != null ? new Dictionary<string, OpenApiExample>(header.Examples) : null;
+            Content = header?.Content != null ? new Dictionary<string, OpenApiMediaType>(header.Content) : null;
+            Extensions = header?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(header.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiInfo.cs b/src/Microsoft.OpenApi/Models/OpenApiInfo.cs
index c5a44c448..df0aa0a49 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiInfo.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiInfo.cs
@@ -59,13 +59,13 @@ public OpenApiInfo() {}
         /// </summary>
         public OpenApiInfo(OpenApiInfo info)
         {
-            Title = info.Title;
-            Description = info.Description;
-            Version = info.Version;
-            TermsOfService = info.TermsOfService;
-            Contact = new(info.Contact);
-            License = new(info.License);
-            Extensions = new Dictionary<string, IOpenApiExtension>(info.Extensions);
+            Title = info?.Title ?? Title;
+            Description = info?.Description ?? Description;
+            Version = info?.Version ?? Version;
+            TermsOfService = info?.TermsOfService ?? TermsOfService;
+            Contact = info?.Contact != null ? new(info?.Contact) : null;
+            License = info?.License != null ? new(info?.License) : null;
+            Extensions = info?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(info.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiLicense.cs b/src/Microsoft.OpenApi/Models/OpenApiLicense.cs
index 431789aac..1a8d1a4d8 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiLicense.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiLicense.cs
@@ -39,9 +39,9 @@ public OpenApiLicense() {}
         /// </summary>
         public OpenApiLicense(OpenApiLicense license)
         {
-            Name = license.Name;
-            Url = new Uri(license.Url.OriginalString);
-            Extensions = new Dictionary<string, IOpenApiExtension>(license.Extensions);
+            Name = license?.Name ?? Name;
+            Url = license?.Url != null ? new Uri(license.Url.OriginalString) : null;
+            Extensions = license?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(license.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiLink.cs b/src/Microsoft.OpenApi/Models/OpenApiLink.cs
index 6ba3a65fd..b682744e9 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiLink.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiLink.cs
@@ -71,15 +71,15 @@ public OpenApiLink() {}
         /// </summary>
         public OpenApiLink(OpenApiLink link)
         {
-            OperationRef = link.OperationRef;
-            OperationId = link.OperationId;
-            Parameters = new(link.Parameters);
-            RequestBody = new(link.RequestBody);
-            Description = link.Description;
-            Server = new(link.Server);
-            Extensions = new Dictionary<string, IOpenApiExtension>(link.Extensions);
-            UnresolvedReference = link.UnresolvedReference;
-            Reference = new(link.Reference);
+            OperationRef = link?.OperationRef ?? OperationRef;
+            OperationId = link?.OperationId ?? OperationId;
+            Parameters = link?.Parameters != null ? new(link?.Parameters) : null;
+            RequestBody = link?.RequestBody != null ? new(link?.RequestBody) : null;
+            Description = link?.Description ?? Description;
+            Server = link?.Server != null ? new(link?.Server) : null;
+            Extensions = link?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(link.Extensions) : null;
+            UnresolvedReference = link?.UnresolvedReference ?? UnresolvedReference;
+            Reference = link?.Reference != null ? new(link?.Reference) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs b/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
index 94dcbdfa7..63a58cd02 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
@@ -53,11 +53,11 @@ public OpenApiMediaType() {}
         /// </summary>
         public OpenApiMediaType(OpenApiMediaType mediaType)
         {
-            Schema = new(mediaType.Schema);
-            Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(mediaType.Example);
-            Examples = new Dictionary<string, OpenApiExample>(mediaType.Examples);
-            Encoding = new Dictionary<string, OpenApiEncoding>(mediaType.Encoding);
-            Extensions = new Dictionary<string, IOpenApiExtension>(mediaType.Extensions);
+            Schema = mediaType?.Schema != null ? new(mediaType?.Schema) : null;
+            Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(mediaType?.Example);
+            Examples = mediaType?.Examples != null ? new Dictionary<string, OpenApiExample>(mediaType.Examples) : null;
+            Encoding = mediaType?.Encoding != null ? new Dictionary<string, OpenApiEncoding>(mediaType.Encoding) : null;
+            Extensions = mediaType?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(mediaType.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiOAuthFlow.cs b/src/Microsoft.OpenApi/Models/OpenApiOAuthFlow.cs
index 02856d4cd..c6f91fbd8 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiOAuthFlow.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiOAuthFlow.cs
@@ -51,11 +51,11 @@ public OpenApiOAuthFlow() {}
         /// </summary>
         public OpenApiOAuthFlow(OpenApiOAuthFlow oAuthFlow)
         {
-            AuthorizationUrl = new Uri(oAuthFlow.AuthorizationUrl.OriginalString);
-            TokenUrl = new Uri(oAuthFlow.TokenUrl.OriginalString);
-            RefreshUrl = new Uri(oAuthFlow.RefreshUrl.OriginalString);
-            Scopes = new Dictionary<string, string>(oAuthFlow.Scopes);
-            Extensions = new Dictionary<string, IOpenApiExtension>(oAuthFlow.Extensions);
+            AuthorizationUrl = oAuthFlow?.AuthorizationUrl != null ? new Uri(oAuthFlow.AuthorizationUrl.OriginalString) : null;
+            TokenUrl = oAuthFlow?.TokenUrl != null ? new Uri(oAuthFlow.TokenUrl.OriginalString) : null;
+            RefreshUrl = oAuthFlow?.RefreshUrl != null ? new Uri(oAuthFlow.RefreshUrl.OriginalString) : null;
+            Scopes = oAuthFlow?.Scopes != null ? new Dictionary<string, string>(oAuthFlow.Scopes) : null;
+            Extensions = oAuthFlow?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(oAuthFlow.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiOAuthFlows.cs b/src/Microsoft.OpenApi/Models/OpenApiOAuthFlows.cs
index 973a403e0..8443e6730 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiOAuthFlows.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiOAuthFlows.cs
@@ -49,11 +49,11 @@ public OpenApiOAuthFlows() {}
         /// <param name="oAuthFlows"></param>
         public OpenApiOAuthFlows(OpenApiOAuthFlows oAuthFlows)
         {
-            Implicit = new(oAuthFlows.Implicit);
-            Password = new(oAuthFlows.Password);
-            ClientCredentials = new(oAuthFlows.ClientCredentials);
-            AuthorizationCode = new(oAuthFlows.AuthorizationCode);
-            Extensions = new Dictionary<string, IOpenApiExtension>(oAuthFlows.Extensions);
+            Implicit = oAuthFlows?.Implicit != null ? new(oAuthFlows?.Implicit) : null;
+            Password = oAuthFlows?.Password != null ? new(oAuthFlows?.Password) : null;
+            ClientCredentials = oAuthFlows?.ClientCredentials != null ? new(oAuthFlows?.ClientCredentials) : null;
+            AuthorizationCode = oAuthFlows?.AuthorizationCode != null ? new(oAuthFlows?.AuthorizationCode) : null;
+            Extensions = oAuthFlows?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(oAuthFlows.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiOperation.cs b/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
index 775532684..ba0af7317 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
@@ -116,19 +116,19 @@ public OpenApiOperation() {}
         /// </summary>
         public OpenApiOperation(OpenApiOperation operation)
         {
-            Tags = new List<OpenApiTag>(operation.Tags);
-            Summary = operation.Summary;
-            Description = operation.Description;
-            ExternalDocs = new(operation.ExternalDocs);
-            OperationId = operation.OperationId;
-            Parameters = new List<OpenApiParameter>(operation.Parameters);
-            RequestBody = new(operation.RequestBody);
-            Responses = new(operation.Responses);
-            Callbacks = new Dictionary<string, OpenApiCallback>(operation.Callbacks);
-            Deprecated = operation.Deprecated;
-            Security = new List<OpenApiSecurityRequirement>(operation.Security);
-            Servers = new List<OpenApiServer>(operation.Servers);
-            Extensions = new Dictionary<string, IOpenApiExtension>(operation.Extensions);
+            Tags = new List<OpenApiTag>(operation?.Tags);
+            Summary = operation?.Summary ?? Summary;
+            Description = operation?.Description ?? Description;
+            ExternalDocs = operation?.ExternalDocs != null ? new(operation?.ExternalDocs) : null;
+            OperationId = operation?.OperationId ?? OperationId;
+            Parameters = operation?.Parameters != null ? new List<OpenApiParameter>(operation.Parameters) : null;
+            RequestBody = new(operation?.RequestBody);
+            Responses = operation?.Responses != null ? new(operation?.Responses) : null;
+            Callbacks = operation?.Callbacks != null ? new Dictionary<string, OpenApiCallback>(operation.Callbacks) : null;
+            Deprecated = operation?.Deprecated ?? Deprecated;
+            Security = operation?.Security != null ? new List<OpenApiSecurityRequirement>(operation.Security) : null;
+            Servers = operation?.Servers != null ? new List<OpenApiServer>(operation.Servers) : null;
+            Extensions = operation?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(operation.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiParameter.cs b/src/Microsoft.OpenApi/Models/OpenApiParameter.cs
index f0b21b0d9..c6f06b1f6 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiParameter.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiParameter.cs
@@ -146,22 +146,22 @@ public OpenApiParameter() {}
         /// </summary>
         public OpenApiParameter(OpenApiParameter parameter)
         {
-            UnresolvedReference = parameter.UnresolvedReference;
-            Reference = new(parameter.Reference);
-            Name = parameter.Name;
-            In = parameter.In;
-            Description = parameter.Description;
-            Required = parameter.Required;
-            Style = parameter.Style;
-            Explode = parameter.Explode;
-            AllowReserved = parameter.AllowReserved;
-            Schema = new(parameter.Schema);
-            Examples = new Dictionary<string, OpenApiExample>(parameter.Examples);
-            Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(parameter.Example);
-            Content = new Dictionary<string, OpenApiMediaType>(parameter.Content);
-            Extensions = new Dictionary<string, IOpenApiExtension>(parameter.Extensions);
-            AllowEmptyValue = parameter.AllowEmptyValue;
-            Deprecated = parameter.Deprecated;
+            UnresolvedReference = parameter?.UnresolvedReference ?? UnresolvedReference;
+            Reference = parameter?.Reference != null ? new(parameter?.Reference) : null;
+            Name = parameter?.Name ?? Name;
+            In = parameter?.In ?? In;
+            Description = parameter?.Description ?? Description;
+            Required = parameter?.Required ?? Required;
+            Style = parameter?.Style ?? Style;
+            Explode = parameter?.Explode ?? Explode;
+            AllowReserved = parameter?.AllowReserved ?? AllowReserved;
+            Schema = parameter?.Schema != null ? new(parameter?.Schema) : null;
+            Examples = parameter?.Examples != null ? new Dictionary<string, OpenApiExample>(parameter.Examples) : null;
+            Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(parameter?.Example);
+            Content = parameter?.Content != null ? new Dictionary<string, OpenApiMediaType>(parameter.Content) : null;
+            Extensions = parameter?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(parameter.Extensions) : null;
+            AllowEmptyValue = parameter?.AllowEmptyValue ?? AllowEmptyValue;
+            Deprecated = parameter?.Deprecated ?? Deprecated;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiPathItem.cs b/src/Microsoft.OpenApi/Models/OpenApiPathItem.cs
index 8ce83c9eb..ddd358dc2 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiPathItem.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiPathItem.cs
@@ -75,14 +75,14 @@ public OpenApiPathItem() {}
         /// </summary>
         public OpenApiPathItem(OpenApiPathItem pathItem)
         {
-            Summary = pathItem.Summary;
-            Description = pathItem.Description;
-            Operations = new Dictionary<OperationType, OpenApiOperation>(pathItem.Operations);
-            Servers = new List<OpenApiServer>(pathItem.Servers);
-            Parameters = new List<OpenApiParameter>(pathItem.Parameters);
-            Extensions = new Dictionary<string, IOpenApiExtension>(pathItem.Extensions);
-            UnresolvedReference = pathItem.UnresolvedReference;
-            Reference = new(pathItem.Reference);
+            Summary = pathItem?.Summary ?? Summary;
+            Description = pathItem?.Description ?? Description;
+            Operations = pathItem?.Operations != null ? new Dictionary<OperationType, OpenApiOperation>(pathItem.Operations) : null;
+            Servers = pathItem?.Servers != null ? new List<OpenApiServer>(pathItem.Servers) : null;
+            Parameters = pathItem?.Parameters != null ? new List<OpenApiParameter>(pathItem.Parameters) : null;
+            Extensions = pathItem?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(pathItem.Extensions) : null;
+            UnresolvedReference = pathItem?.UnresolvedReference ?? UnresolvedReference;
+            Reference = pathItem?.Reference != null ? new(pathItem?.Reference) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiReference.cs b/src/Microsoft.OpenApi/Models/OpenApiReference.cs
index 9213e77bc..31cc5a6e8 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiReference.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiReference.cs
@@ -122,10 +122,10 @@ public OpenApiReference() {}
         /// </summary>
         public OpenApiReference(OpenApiReference reference)
         {
-            ExternalResource = reference.ExternalResource;
-            Type = reference.Type;
-            Id = reference.Id;
-            HostDocument = new(reference.HostDocument);
+            ExternalResource = reference?.ExternalResource;
+            Type = reference?.Type;
+            Id = reference?.Id;
+            HostDocument = new(reference?.HostDocument);
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiRequestBody.cs b/src/Microsoft.OpenApi/Models/OpenApiRequestBody.cs
index b82b67e8a..9016fd7a3 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiRequestBody.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiRequestBody.cs
@@ -55,12 +55,12 @@ public OpenApiRequestBody() { }
         /// </summary>
         public OpenApiRequestBody(OpenApiRequestBody requestBody)
         {
-            UnresolvedReference = requestBody.UnresolvedReference;
-            Reference = new(requestBody.Reference);
-            Description = requestBody.Description;
-            Required = requestBody.Required;
-            Content = new Dictionary<string, OpenApiMediaType>(requestBody.Content);
-            Extensions = new Dictionary<string, IOpenApiExtension>(requestBody.Extensions);
+            UnresolvedReference = requestBody?.UnresolvedReference ?? UnresolvedReference;
+            Reference = requestBody?.Reference != null ? new(requestBody?.Reference) : null;
+            Description = requestBody?.Description ?? Description;
+            Required = requestBody?.Required ?? Required;
+            Content = requestBody?.Content != null ? new Dictionary<string, OpenApiMediaType>(requestBody.Content) : null;
+            Extensions = requestBody?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(requestBody.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiResponse.cs b/src/Microsoft.OpenApi/Models/OpenApiResponse.cs
index cf0c796e6..a173f6c1a 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiResponse.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiResponse.cs
@@ -61,13 +61,13 @@ public OpenApiResponse() {}
         /// </summary>
         public OpenApiResponse(OpenApiResponse response)
         {
-            Description = response.Description;
-            Headers = new Dictionary<string, OpenApiHeader>(response.Headers);
-            Content = new Dictionary<string, OpenApiMediaType>(response.Content);
-            Links = new Dictionary<string, OpenApiLink>(response.Links);
-            Extensions = new Dictionary<string, IOpenApiExtension>(response.Extensions);
-            UnresolvedReference = response.UnresolvedReference;
-            Reference = new(response.Reference);
+            Description = response?.Description ?? Description;
+            Headers = response?.Headers != null ? new Dictionary<string, OpenApiHeader>(response.Headers) : null;
+            Content = response?.Content != null ? new Dictionary<string, OpenApiMediaType>(response.Content) : null;
+            Links = response?.Links != null ? new Dictionary<string, OpenApiLink>(response.Links) : null;
+            Extensions = response?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(response.Extensions) : null;
+            UnresolvedReference = response?.UnresolvedReference ?? UnresolvedReference;
+            Reference = response?.Reference != null ? new(response?.Reference) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiSchema.cs b/src/Microsoft.OpenApi/Models/OpenApiSchema.cs
index d43756887..3886a5555 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiSchema.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiSchema.cs
@@ -252,44 +252,44 @@ public OpenApiSchema() {}
         /// </summary>
         public OpenApiSchema(OpenApiSchema schema)
         {
-            Title = schema.Title;
-            Type = schema.Type;
-            Format = schema.Format;
-            Description = schema.Description;
-            Maximum = schema.Maximum;
-            ExclusiveMaximum = schema.ExclusiveMaximum;
-            Minimum = schema.Minimum;
-            ExclusiveMinimum = schema.ExclusiveMinimum;
-            MaxLength = schema.MaxLength;
-            MinLength = schema.MinLength;
-            Pattern = schema.Pattern;
-            MultipleOf = schema.MultipleOf;
-            Default = OpenApiAnyCloneHelper.CloneFromCopyConstructor(schema.Default);
-            ReadOnly = schema.ReadOnly;
-            WriteOnly = schema.WriteOnly;
-            AllOf = new List<OpenApiSchema>(schema.AllOf);
-            OneOf = new List<OpenApiSchema>(schema.OneOf);
-            AnyOf = new List<OpenApiSchema>(schema.AnyOf);
-            Not = new(schema.Not);
-            Required = new HashSet<string>(schema.Required);
-            Items = new(schema.Items);
-            MaxItems = schema.MaxItems;
-            MinItems = schema.MinItems;
-            UniqueItems = schema.UniqueItems;
-            Properties = new Dictionary<string, OpenApiSchema>(schema.Properties);
-            MaxProperties = schema.MaxProperties;
-            MinProperties = schema.MinProperties;
-            AdditionalPropertiesAllowed = schema.AdditionalPropertiesAllowed;
-            AdditionalProperties = new(schema.AdditionalProperties);
-            Discriminator = new(schema.Discriminator);
-            Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(schema.Example);
-            Enum = new List<IOpenApiAny>(schema.Enum);
-            Nullable = schema.Nullable;
-            ExternalDocs = new(schema.ExternalDocs);
-            Deprecated = schema.Deprecated;
-            Xml = new(schema.Xml);
-            UnresolvedReference = schema.UnresolvedReference;
-            Reference = new(schema.Reference);
+            Title = schema?.Title ?? Title;
+            Type = schema?.Type ?? Type;
+            Format = schema?.Format ?? Format;
+            Description = schema?.Description ?? Description;
+            Maximum = schema?.Maximum ?? Maximum;
+            ExclusiveMaximum = schema?.ExclusiveMaximum ?? ExclusiveMaximum;
+            Minimum = schema?.Minimum ?? Minimum;
+            ExclusiveMinimum = schema?.ExclusiveMinimum ?? ExclusiveMinimum;
+            MaxLength = schema?.MaxLength ?? MaxLength;
+            MinLength = schema?.MinLength ?? MinLength;
+            Pattern = schema?.Pattern ?? Pattern;
+            MultipleOf = schema?.MultipleOf ?? MultipleOf;
+            Default = OpenApiAnyCloneHelper.CloneFromCopyConstructor(schema?.Default);
+            ReadOnly = schema?.ReadOnly ?? ReadOnly;
+            WriteOnly = schema?.WriteOnly ?? WriteOnly;
+            AllOf = schema?.AllOf != null ? new List<OpenApiSchema>(schema.AllOf) : null;
+            OneOf = schema?.OneOf != null ? new List<OpenApiSchema>(schema.OneOf) : null;
+            AnyOf = schema?.AnyOf != null ? new List<OpenApiSchema>(schema.AnyOf) : null;
+            Not = schema?.Not != null ? new(schema?.Not) : null;
+            Required = schema?.Required != null ? new HashSet<string>(schema.Required) : null;
+            Items = schema?.Items != null ? new(schema?.Items) : null;
+            MaxItems = schema?.MaxItems ?? MaxItems;
+            MinItems = schema?.MinItems ?? MinItems;
+            UniqueItems = schema?.UniqueItems ?? UniqueItems;
+            Properties = schema?.Properties != null ? new Dictionary<string, OpenApiSchema>(schema.Properties) : null;
+            MaxProperties = schema?.MaxProperties ?? MaxProperties;
+            MinProperties = schema?.MinProperties ?? MinProperties;
+            AdditionalPropertiesAllowed = schema?.AdditionalPropertiesAllowed ?? AdditionalPropertiesAllowed;
+            AdditionalProperties = new(schema?.AdditionalProperties);
+            Discriminator = schema?.Discriminator != null ? new(schema?.Discriminator) : null;
+            Example = OpenApiAnyCloneHelper.CloneFromCopyConstructor(schema?.Example);
+            Enum = schema?.Enum != null ? new List<IOpenApiAny>(schema.Enum) : null;
+            Nullable = schema?.Nullable ?? Nullable;
+            ExternalDocs = schema?.ExternalDocs != null ? new(schema?.ExternalDocs) : null;
+            Deprecated = schema?.Deprecated ?? Deprecated;
+            Xml = schema?.Xml != null ? new(schema?.Xml) : null;
+            UnresolvedReference = schema?.UnresolvedReference ?? UnresolvedReference;
+            Reference = schema?.Reference != null ? new(schema?.Reference) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiSecurityScheme.cs b/src/Microsoft.OpenApi/Models/OpenApiSecurityScheme.cs
index b87adf573..913e70441 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiSecurityScheme.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiSecurityScheme.cs
@@ -84,17 +84,17 @@ public OpenApiSecurityScheme() {}
         /// </summary>
         public OpenApiSecurityScheme(OpenApiSecurityScheme securityScheme)
         {
-            Type = securityScheme.Type;
-            Description = securityScheme.Description;
-            Name = securityScheme.Name;
-            In = securityScheme.In;
-            Scheme = securityScheme.Scheme;
-            BearerFormat = securityScheme.BearerFormat;
-            Flows = new(securityScheme.Flows);
-            OpenIdConnectUrl = new Uri(securityScheme.OpenIdConnectUrl.OriginalString);
-            Extensions = new Dictionary<string, IOpenApiExtension>(securityScheme.Extensions);
-            UnresolvedReference = securityScheme.UnresolvedReference;
-            Reference = new(securityScheme.Reference);
+            Type = securityScheme?.Type ?? Type;
+            Description = securityScheme?.Description ?? Description;
+            Name = securityScheme?.Name ?? Name;
+            In = securityScheme?.In ?? In;
+            Scheme = securityScheme?.Scheme ?? Scheme;
+            BearerFormat = securityScheme?.BearerFormat ?? BearerFormat;
+            Flows = securityScheme?.Flows != null ? new(securityScheme?.Flows) : null;
+            OpenIdConnectUrl = securityScheme?.OpenIdConnectUrl != null ? new Uri(securityScheme.OpenIdConnectUrl.OriginalString) : null;
+            Extensions = securityScheme?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(securityScheme.Extensions) : null;
+            UnresolvedReference = securityScheme?.UnresolvedReference ?? UnresolvedReference;
+            Reference = securityScheme?.Reference != null ? new(securityScheme?.Reference) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiServer.cs b/src/Microsoft.OpenApi/Models/OpenApiServer.cs
index 875bef5c7..b3b1d1287 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiServer.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiServer.cs
@@ -46,10 +46,10 @@ public OpenApiServer() {}
         /// </summary>
         public OpenApiServer(OpenApiServer server)
         {
-            Description = server.Description;
-            Url = server.Url;
-            Variables = new Dictionary<string, OpenApiServerVariable>(server.Variables);
-            Extensions = new Dictionary<string, IOpenApiExtension>(server.Extensions);
+            Description = server?.Description ?? Description;
+            Url = server?.Url ?? Url;
+            Variables = server?.Variables != null ? new Dictionary<string, OpenApiServerVariable>(server.Variables) : null;
+            Extensions = server?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(server.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiServerVariable.cs b/src/Microsoft.OpenApi/Models/OpenApiServerVariable.cs
index b1f222e83..70164bc59 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiServerVariable.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiServerVariable.cs
@@ -44,10 +44,10 @@ public OpenApiServerVariable() {}
         /// </summary>
         public OpenApiServerVariable(OpenApiServerVariable serverVariable)
         {
-            Description = serverVariable.Description;
-            Default = serverVariable.Default;
-            Enum = new List<string>(serverVariable.Enum);
-            Extensions = new Dictionary<string, IOpenApiExtension>(serverVariable.Extensions);
+            Description = serverVariable?.Description;
+            Default = serverVariable?.Default;
+            Enum = serverVariable?.Enum != null ? new List<string>(serverVariable?.Enum) : serverVariable?.Enum;
+            Extensions = serverVariable?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(serverVariable?.Extensions) : serverVariable?.Extensions;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiTag.cs b/src/Microsoft.OpenApi/Models/OpenApiTag.cs
index 5ecfa0363..ba4129142 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiTag.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiTag.cs
@@ -53,12 +53,12 @@ public OpenApiTag() {}
         /// </summary>
         public OpenApiTag(OpenApiTag tag)
         {
-            Name = tag.Name;
-            Description = tag.Description;
-            ExternalDocs = new(tag.ExternalDocs);
-            Extensions = new Dictionary<string, IOpenApiExtension>(tag.Extensions);
-            UnresolvedReference = tag.UnresolvedReference;
-            Reference = new(tag.Reference);
+            Name = tag?.Name ?? Name;
+            Description = tag?.Description ?? Description;
+            ExternalDocs = tag?.ExternalDocs != null ? new(tag?.ExternalDocs) : null;
+            Extensions = tag?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(tag.Extensions) : null;
+            UnresolvedReference = tag?.UnresolvedReference ?? UnresolvedReference;
+            Reference = tag?.Reference != null ? new(tag?.Reference) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiXml.cs b/src/Microsoft.OpenApi/Models/OpenApiXml.cs
index eb48132ad..c6719d85e 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiXml.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiXml.cs
@@ -56,12 +56,12 @@ public OpenApiXml() {}
         /// </summary>
         public OpenApiXml(OpenApiXml xml)
         {
-            Name = xml.Name;
-            Namespace = xml.Namespace;
-            Prefix = xml.Prefix;
-            Attribute = xml.Attribute;
-            Wrapped = xml.Wrapped;
-            Extensions = new Dictionary<string, IOpenApiExtension>(xml.Extensions);
+            Name = xml?.Name ?? Name;
+            Namespace = xml?.Namespace ?? Namespace;
+            Prefix = xml?.Prefix ?? Prefix;
+            Attribute = xml?.Attribute ?? Attribute;
+            Wrapped = xml?.Wrapped ?? Wrapped;
+            Extensions = xml?.Extensions != null ? new Dictionary<string, IOpenApiExtension>(xml.Extensions) : null;
         }
 
         /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/RuntimeExpressionAnyWrapper.cs b/src/Microsoft.OpenApi/Models/RuntimeExpressionAnyWrapper.cs
index 85c64dd30..1a1f12a18 100644
--- a/src/Microsoft.OpenApi/Models/RuntimeExpressionAnyWrapper.cs
+++ b/src/Microsoft.OpenApi/Models/RuntimeExpressionAnyWrapper.cs
@@ -26,8 +26,8 @@ public RuntimeExpressionAnyWrapper() {}
         /// </summary>
         public RuntimeExpressionAnyWrapper(RuntimeExpressionAnyWrapper runtimeExpressionAnyWrapper)
         {
-            Any = OpenApiAnyCloneHelper.CloneFromCopyConstructor(runtimeExpressionAnyWrapper.Any);
-            Expression = runtimeExpressionAnyWrapper.Expression;
+            Any = OpenApiAnyCloneHelper.CloneFromCopyConstructor(runtimeExpressionAnyWrapper?.Any);
+            Expression = runtimeExpressionAnyWrapper?.Expression;
         }
 
         /// <summary>