怎么利用c#修改services的Startup type

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Management;

namespace ServicesStartup
{
    class Program
    {
        public enum StartupType
        {
            Automatic,
            Disabled,
            Manual
        }

        public static void SetStartupType(string serviceName, StartupType startupType)
        {
            string type = startupType.ToString();
            try
            {
                ManagementPath mp = new ManagementPath(string.Format("Win32_Service.Name='{0}'", serviceName));
                if (mp != null)
                {
                    using (ManagementObject mo = new ManagementObject(mp))
                    {
                        object[] parameters = new object[1] { type };
                        mo.InvokeMethod("ChangeStartMode", parameters);                       
                    }
                }
            }
            catch (ManagementException ex)
            {
                Console.WriteLine("An error occured while trying to searching the WMI method: " + ex.ToString());
            }

        }

        static void Main(string[] args)
        {
            SetStartupType("gupdate", StartupType.Automatic); 
            Console.ReadKey();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Management;

namespace ServicesStartup
{
    class Program
    {
       static void Main(string[] args)
        {
            try
            {
                ManagementObject classInstance = new ManagementObject("root\\CIMV2",
                    "Win32_Service.Name='gupdate'", null);

                // Obtain in-parameters for the method.
                ManagementBaseObject inParams = classInstance.GetMethodParameters("ChangeStartMode");
                // Add the input parameters.
                inParams["StartMode"] = "Automatic";               

                // Execute the method and obtain the return values.
                ManagementBaseObject outParams = classInstance.InvokeMethod("ChangeStartMode", inParams, null);

                // List outParams
                Console.WriteLine("Out parameters:");
                Console.WriteLine("ReturnValue: " + outParams["ReturnValue"]);
            }
            catch (ManagementException err)
            {
                Console.WriteLine("An error occured while trying to execute the WMI emthod: " + err.ToString());
            }
            Console.ReadKey();
        }
    }
}