// @nuget: CommandLineParser -Version 2.5.0

/*

https://github.com/commandlineparser/commandline/issues/104#issuecomment-493714241

When outputting HelpText, the following code will correctly list valid values for enum type options. However, if the option is a nullable enum type, then it will not list the valid values.

is this a bug, or is there another setting/workaround for nullable enums?

*/

​

using System;

using System.Collections.Generic;

using CommandLine;

using CommandLine.Text;

using System.Linq;

using System.Threading.Tasks;

​

using System;

public class Program

{

    public static void Main()

    {       

        //Console.SetError(Console.Out);

        Console.WriteLine("CommandLineParser 2.5");

        var args ="-f".Split();

        var parser= new Parser(config=>config.HelpWriter= null);

    var parserResult = parser.ParseArguments<Options>(args);

    parserResult

    .WithParsed(option => HandleOptions(option))

    .WithNotParsed(errors =>

{

    // Use custom help text to ensure valid enum values are displayed

    var helpText = HelpText.AutoBuild(parserResult);

    helpText.AddEnumValuesToHelpText = true;

    helpText.AddOptions(parserResult);

    Console.Write(helpText);

    //Environment.Exit(1);//in dotnetfiddle, raise exception Run-time exception (line -1): Request for the permission of type 'System.Security.Permissions.SecurityPermission, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.

​

});

    }

    static void HandleOptions(Options option )

{

  Console.WriteLine(option.MyFeature);

}

}

//-------

​

 class Options {

      [Option('f', "myfeature", HelpText = "Path to the myfeature.")]

      public Feature? MyFeature { get; set; }

  }

enum Feature

{

One,

Two,

Three

}