Test.cs

using System;
using System.Threading.Tasks;

namespace ArgTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var h = new Humidifier();

            h.SetModeAsync("id", DeviceMode.Auto);
            h.SetModeAsync("id", DeviceMode.Value101);
            h.SetModeAsync("id", DeviceMode.Value102);
            h.SetModeAsync("id", DeviceMode.Value103);
            h.SetModeAsync("id", DeviceMode.PercentageMode(33));
        }

    }

    public class Humidifier
    {
        public Task<CommandExecuteResoponse> SetModeAsync(string deviceId, DeviceMode mode)
        {
            var parameter = mode.Value;

            return Task.FromResult(new CommandExecuteResoponse());
        }
    }

    public struct DeviceMode
    {
        private static DeviceMode s_auto = new DeviceMode("auto");
        private static DeviceMode s_101 = new DeviceMode("101");
        private static DeviceMode s_102 = new DeviceMode("102");
        private static DeviceMode s_103 = new DeviceMode("103");
        public string Value { get; }

        DeviceMode(string value)
        {
            Value = value;
        }

        public static DeviceMode PercentageMode(int percentage)
        {
            if (percentage < 0 || percentage > 100) { throw new ArgumentOutOfRangeException(nameof(percentage)); }
            return new DeviceMode(percentage.ToString());
        }

        public static DeviceMode Auto => s_auto;
        public static DeviceMode Value101 => s_101;
        public static DeviceMode Value102 => s_102;
        public static DeviceMode Value103 => s_103;
    }
}