Sharepoint administrator adding

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.SharePoint;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {

            SPSite site = new SPSite("http://kn-dev/");

            SPWeb web = site.RootWeb;
            {
                web.AllowUnsafeUpdates = true;
                web.AllUsers.Add("axisspecialty\\service-spadmin-d", "service-spadmin-d", "service-spadmin-d", null);
                SPUser spUser = web.SiteUsers["axisspecialty\\service-spadmin-d"];

                spUser.IsSiteAdmin = true;

                spUser.Update();

                web.AllowUnsafeUpdates = false;
            }


        }
    }



}