Code sample for https://github.com/dotnet/command-line-api/issues/1691

Program.cs

using System.CommandLine;
using System.CommandLine.Builder;
using System.CommandLine.Help;
using System.CommandLine.NamingConventionBinder;

namespace SysCmdLine
{
    class Program
    {
        public static void Main(string[] args)
        {

            RootCommand rootCommand = new RootCommand(description: "Sample code to show Issue #1691");

            var testCommand = new Command("test", "Simple test command")
            {
                new Option<string>(new string[]{"--opt1", "--o1"}, "Option 1"),
                new Option<string>(new string[]{"--opt2", "--o2"}, "Option 1"),
            };
            testCommand.Handler = CommandHandler.Create<string, string>(Worker.RunTest);

            rootCommand.Add(testCommand);


            var parser = new CommandLineBuilder(rootCommand)
                .UseDefaults()
                .UseHelp(ctx =>
                {
                    ctx.HelpBuilder.CustomizeLayout(_ => System.CommandLine.Help.HelpBuilder.Default
                                             .GetLayout()
                                             .Prepend(
                                                 _ => _.Output.WriteLine("**Adding extra help here**")
                                             ));
                }).Build();

            rootCommand.InvokeAsync(args).Wait();
        }
        public class Worker
        {
            public static void RunTest(string opt1, string opt2)
            {
                Console.WriteLine(opt1);
                Console.WriteLine(opt2);
            }
        }
    }
}

SysCmdLine.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Hosting" Version="6.0.1" />
    <PackageReference Include="System.CommandLine" Version="2.0.0-beta3.22114.1" />
    <PackageReference Include="System.CommandLine.NamingConventionBinder" Version="2.0.0-beta3.22114.1" />
  </ItemGroup>

</Project>