OpenAPITools/openapi-generator · error · IllegalArgumentException

Invalid model property naming '{name}'. Must be 'original',

Error message

Invalid model property naming '{name}'. Must be 'original', 'camelCase', 'PascalCase' or 'snake_case'

What it means

Error "Invalid model property naming '{name}'. Must be 'original', 'camelCase', 'PascalCase' or 'snake_case'" thrown in OpenAPITools/openapi-generator.

Source

Thrown at modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java:641

    }

    @Override
    public String getName() {
        return "csharp";
    }

    public String getNameUsingModelPropertyNaming(String name) {
        switch (CodegenConstants.MODEL_PROPERTY_NAMING_TYPE.valueOf(getModelPropertyNaming())) {
            case original:
                return name;
            case camelCase:
                return camelize(name, LOWERCASE_FIRST_LETTER);
            case PascalCase:
                return camelize(name);
            case snake_case:
                return underscore(name);
            default:
                throw new IllegalArgumentException("Invalid model property naming '" +
                        name + "'. Must be 'original', 'camelCase', " +
                        "'PascalCase' or 'snake_case'");
        }
    }

    @Override
    public String getNullableType(Schema p, String type) {
        if (GENERICHOST.equals(getLibrary())) {
            return super.getNullableType(p, type);
        }

        if (languageSpecificPrimitives.contains(type)) {
            if (isSupportNullable() && ModelUtils.isNullable(p) && this.getNullableTypes().contains(type)) {
                return type + "?";
            } else {
                return type;
            }
        } else {

View on GitHub (pinned to fcec517be3)

Solutions

1. Set modelPropertyNaming to one of 'original', 'camelCase', 'PascalCase' or 'snake_case'.

When it happens

Trigger: Thrown when the model property naming option for the C# client generator is not 'original', 'camelCase', 'PascalCase' or 'snake_case'.

Common situations: See trigger scenarios.

AI-assisted analysis of OpenAPITools/openapi-generator@fcec517be3 (2026-08-22). Data as JSON: /api/errors/a07c6cc45e0a7f0f. Report an issue: GitHub.