[Bug]: Client serialization does not preserve the API's expected JSON property names and enum representation

Description

The OpenAPI specification defines the request body using camelCase property names and the lowercase enum value "available". The generated client produces a different representation.

Swagger Codegen Version

3.0.82

Language / Generator

• csharp

OpenAPI/Swagger Spec

{
    "openapi": "3.0.0",
    "info": {
        "title": "Serializer Test API",
        "version": "0.0.0"
    },
    "tags": [
        {
            "name": "test",
            "description": "Serializer test operations"
        }
    ],
    "paths": {
        "/test": {
            "post": {
                "tags": [
                    "test"
                ],
                "operationId": "post_test_xcuctqa",
                "summary": "Test model serialization",
                "requestBody": {
                    "required": true,
                    "content": {
                        "application/json": {
                            "schema": {
                                "$ref": "#/components/schemas/TestModel"
                            }
                        }
                    }
                },
                "responses": {
                    "200": {
                        "description": "OK"
                    }
                }
            }
        }
    },
    "components": {
        "schemas": {
            "TestModel": {
                "type": "object",
                "properties": {
                    "id": {
                        "type": "integer",
                        "format": "int64"
                    },
                    "firstName": {
                        "type": "string"
                    },
                    "optionalValue": {
                        "type": "string"
                    },
                    "status": {
                        "type": "string",
                        "enum": [
                            "available",
                            "pending"
                        ]
                    },
                    "tags": {
                        "type": "array",
                        "items": {
                            "$ref": "#/components/schemas/Tag"
                        }
                    }
                },
                "additionalProperties": false
            },
            "Tag": {
                "type": "object",
                "properties": {
                    "id": {
                        "type": "integer",
                        "format": "int64"
                    },
                    "name": {
                        "type": "string"
                    }
                },
                "additionalProperties": false
            }
        }
    }
}

Command Line Used

I am using a script that uses the basic command

docker run --rm \
    --user "$(id -u):$(id -g)" \
    -v "$(pwd)":/local \
    -v "$PARENT_DIR":/output \
    swaggerapi/swagger-codegen-cli-v3:3.0.82 \
    generate \
    -i /local/spec/openapi.json \
    -l "$LANG" \
    -o "/output/$OUT_NAME"

and in this case uses 'csharp' for $LANG

Steps to Reproduce

1. Generate a client using the provided specification
2. Send a request using

var body = new TestModel
{
    Id = 1,
    FirstName = "test",
    Status = TestModel.StatusEnum.Available
};

await api.PostTestXcuctqaAsync(body);

3. Observe the outgoing request body

Expected Behavior

The serialized request body should use the property names and enum values defined by the OpenAPI specification:

{
"id": 1,
"firstName": "test",
"status": "available"
}

Actual Behavior

The generated client serializes the model as:

{
"Status": "Available",
"Id": 1,
"FirstName": "test",
"OptionalValue": null,
"Tags": null
}

Related Issues / Repos

Environment

• OS: Fedora 43

Additional Context

Checklist

• I have searched the existing issues to make sure this is not a duplicate.
• I have included a minimal and reproducible spec example.
• I have explained how to reproduce the issue.
• I have specified which generator/language is affected.

Start by generating the C# client with the supplied OpenAPI specification and inspect the generated model serialization path. Compare the outgoing JSON with the expected camelCase property names, lowercase enum values, and omitted null fields; done means the reproduced request matches the specification.