Configuration

OpenAPI Code Generator provides a rich set of options to customize the generated C# output. Options can be set via CLI flags or programmatically through GeneratorOptions.

Options Overview

Option	CLI Flag	Default	Description
Namespace	-n, --namespace	GeneratedModels	C# namespace for generated types
GenerateDocComments	--no-doc-comments	true	Include XML doc comments
GenerateFileHeader	--no-header	true	Auto-generated file header
DefaultNonNullable	--no-default-non-nullable	true	Defaults as non-nullable
AddDefaultValuesToProperties	--no-add-default-values	true	Add default values from OpenAPI to properties
UseImmutableArrays	--mutable-arrays	true	Use IReadOnlyList<T>
UseImmutableDictionaries	--mutable-dictionaries	true	Use IReadOnlyDictionary

Namespace

Controls the C# namespace for all generated types.

CLI:

openapi-codegen spec.yaml -o Models.cs -n MyApp.Api.Models

Library:

new GeneratorOptions { Namespace = "MyApp.Api.Models" }

Output:

namespace MyApp.Api.Models;

XML Doc Comments

When enabled, OpenAPI description fields are converted to XML doc comments on the generated types and properties.

CLI: Enabled by default. Disable with --no-doc-comments.

Example output with doc comments:

/// <summary>
/// A pet available in the store
/// </summary>
public record Pet
{
    /// <summary>
    /// The unique identifier for the pet
    /// </summary>
    [JsonPropertyName("id")]
    public long Id { get; init; }
}

Without doc comments:

public record Pet
{
    [JsonPropertyName("id")]
    public long Id { get; init; }
}

File Header

When enabled, adds an auto-generated comment header to prevent accidental manual editing:

// <auto-generated>
// This file was auto-generated by OpenApiCodeGenerator.
// Do not make direct changes to the file.
// </auto-generated>

CLI: Enabled by default. Disable with --no-header.

Default Non-Nullable

When enabled, properties with default values in the OpenAPI spec are treated as non-nullable.

CLI: Enabled by default. Disable with --no-default-non-nullable.

Add Default Values to Properties

When enabled, properties with default values in the OpenAPI spec will have those default values added to the generated C# properties.

CLI: Enabled by default. Disable with --no-add-default-values.

Immutable Collections

Arrays

Controls whether array types use IReadOnlyList<T> (immutable) or List<T> (mutable).

CLI: Immutable by default. Use --mutable-arrays for List<T>.

Immutable (default):

public IReadOnlyList<string> Tags { get; init; }

Mutable:

public List<string> Tags { get; init; }

Dictionaries

Controls whether dictionary types use IReadOnlyDictionary<string, T> or Dictionary<string, T>.

CLI: Immutable by default. Use --mutable-dictionaries for mutable.

Immutable (default):

public IReadOnlyDictionary<string, object> Metadata { get; init; }

Mutable:

public Dictionary<string, object> Metadata { get; init; }