[Test]
    public void
        GivenOa3ContainsOptionalHeaderAndWeUseCancellationToken_WhenGeneratingControllerCSharpCode_ItResultsInNonCompilableCode()
    {
        var yamlDoc = @"
            openapi: 3.0.0
            info:
              title: Sample API
              version: 1.0.0
            paths:
              /users:
                get:
                  summary: Get all users
                  parameters:
                  - name: X-MyHeader
                    in: header
                    required: false
                    schema:
                      type: string
                  responses:
                    '200':
                      description: A list of users
                      content:
                        application/json:
                          schema:
                            type: array
                            items:
                              type: integer";
        CSharpControllerGeneratorSettings settings = new()
        {
            GenerateOptionalParameters = true, UseCancellationToken = true,
        };
        OpenApiDocument? document = OpenApiYamlDocument.FromYamlAsync(yamlDoc).Result;
        var generator = new CSharpControllerGenerator(document, settings);
        string? code = generator.GenerateFile();
        Console.WriteLine($"Generated code:\n{code}.");

        //The Interface (assert passes)
        code.Should()
            .Contain(
                "string x_MyHeader = null, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken));");
        //The implementation (assert fails) - compile error due to " = null"
        code.Should()
            .NotContain(
                "string x_MyHeader = null, System.Threading.CancellationToken cancellationToken)\n");
    }

Generated code:
//----------------------
// <auto-generated>
//     Generated using the NSwag toolchain v14.1.0.0 (NJsonSchema v11.0.2.0 (Newtonsoft.Json v13.0.0.0)) (http://NSwag.org)
// </auto-generated>
//----------------------

#pragma warning disable 108 // Disable "CS0108 '{derivedDto}.ToJson()' hides inherited member '{dtoBase}.ToJson()'. Use the new keyword if hiding was intended."
#pragma warning disable 114 // Disable "CS0114 '{derivedDto}.RaisePropertyChanged(String)' hides inherited member 'dtoBase.RaisePropertyChanged(String)'. To make the current member override that implementation, add the override keyword. Otherwise add the new keyword."
#pragma warning disable 472 // Disable "CS0472 The result of the expression is always 'false' since a value of type 'Int32' is never equal to 'null' of type 'Int32?'
#pragma warning disable 612 // Disable "CS0612 '...' is obsolete"
#pragma warning disable 649 // Disable "CS0649 Field is never assigned to, and will always have its default value null"
#pragma warning disable 1573 // Disable "CS1573 Parameter '...' has no matching param tag in the XML comment for ...
#pragma warning disable 1591 // Disable "CS1591 Missing XML comment for publicly visible type or member ..."
#pragma warning disable 8073 // Disable "CS8073 The result of the expression is always 'false' since a value of type 'T' is never equal to 'null' of type 'T?'"
#pragma warning disable 3016 // Disable "CS3016 Arrays as attribute arguments is not CLS-compliant"
#pragma warning disable 8603 // Disable "CS8603 Possible null reference return"
#pragma warning disable 8604 // Disable "CS8604 Possible null reference argument for parameter"
#pragma warning disable 8625 // Disable "CS8625 Cannot convert null literal to non-nullable reference type"
#pragma warning disable 8765 // Disable "CS8765 Nullability of type of parameter doesn't match overridden member (possibly because of nullability attributes)."

namespace MyNamespace
{
    using System = global::System;

    [System.CodeDom.Compiler.GeneratedCode("NSwag", "14.1.0.0 (NJsonSchema v11.0.2.0 (Newtonsoft.Json v13.0.0.0))")]
    public interface IController
    {

        /// <summary>
        /// Get all users
        /// </summary>


        /// <returns>A list of users</returns>

        System.Threading.Tasks.Task<System.Collections.Generic.ICollection<int>> UsersAsync(string x_MyHeader = null, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken));

    }

    [System.CodeDom.Compiler.GeneratedCode("NSwag", "14.1.0.0 (NJsonSchema v11.0.2.0 (Newtonsoft.Json v13.0.0.0))")]

    public partial class Controller : Microsoft.AspNetCore.Mvc.ControllerBase
    {
        private IController _implementation;

        public Controller(IController implementation)
        {
            _implementation = implementation;
        }

        /// <summary>
        /// Get all users
        /// </summary>
        /// <returns>A list of users</returns>
        [Microsoft.AspNetCore.Mvc.HttpGet, Microsoft.AspNetCore.Mvc.Route("users")]
        public System.Threading.Tasks.Task<System.Collections.Generic.ICollection<int>> Users([Microsoft.AspNetCore.Mvc.FromHeader(Name = "X-MyHeader")] string x_MyHeader = null, System.Threading.CancellationToken cancellationToken)
        {

            return _implementation.UsersAsync(x_MyHeader, cancellationToken);
        }

    }

    


}

#pragma warning restore  108
#pragma warning restore  114
#pragma warning restore  472
#pragma warning restore  612
#pragma warning restore 1573
#pragma warning restore 1591
#pragma warning restore 8073
#pragma warning restore 3016
#pragma warning restore 8603
#pragma warning restore 8604
#pragma warning restore 8625.