public static void Main(string[] args)
        {
            SPWebApplication webapp = SPWebApplication.Lookup(new Uri(http://Hello:9090));
            SPSite spSite = null;
            spSite = webapp.Sites["ssp/admin"];
            SPWeb spWeb = spSite.OpenWeb();

            string strSiteURL = spSite.Url.ToString();
            string strLoginName = @"Hello\tt";
            string strEmail = "";
            string strName = @"HELLO\tt";
            string strNotes = "";
            string strGroup = string.Empty;
            //Get or create user or remove user
            SPUser spUser = GetSPUser(strLoginName, strSiteURL);
            if (spUser == null)
            {
                spUser = CreateUser(strLoginName, strEmail, strName, strNotes, strSiteURL);
            }
            else
            {
                RemoveUser(strLoginName, strSiteURL);
            }
           ////Open group
            //SPGroup spGroup = spWeb.SiteGroups[strGroup];
            //Add and update group with new user
            ////spGroup.AddUser(spUser.LoginName, spUser.Email, spUser.Name, "Added by UserControl");
            //spGroup.Update();
        }

        public static SPUser GetSPUser(string strLoginName, string strSiteURL)
        {
            SPUser spReturn = null;
            SPSite spSite = null;
            SPWeb spWeb = null;
            try
            {
                //Open the SharePoint Site
                spSite = new SPSite(strSiteURL);
                spWeb = spSite.OpenWeb();
                //Check to see if user exists
                spReturn = spWeb.AllUsers[strLoginName];
            }
            catch (Exception)
            {
            }
            finally
            {
                spWeb.Close();
                spSite.Close();
            }
            return spReturn;
        }
        public static SPUser CreateUser(string strLoginName, string strEmail, string strName, string strNotes, string strSiteURL)
        {
            SPUser spReturn = null;
            SPSite spSite = null;
            SPWeb spWeb = null;
            try
            {
                //Open the SharePoint site
                spSite = new SPSite(strSiteURL);
                spWeb = spSite.OpenWeb();
                //Assign role and add user to site
                SPRoleAssignment spRoleAssignment = new SPRoleAssignment(strLoginName, strEmail, strName, strNotes);
                //Using Contribute, might need high access
                SPRoleDefinition spSPRoleDefinition = spWeb.RoleDefinitions["Full Control"];
                spRoleAssignment.RoleDefinitionBindings.Add(spSPRoleDefinition);
                spWeb.RoleAssignments.Add(spRoleAssignment);
              
                //Update site
                spWeb.Update();
                spReturn = spWeb.AllUsers[strLoginName];
            }
            catch (Exception)
            { }
            finally
            {
                spWeb.Close();
                spSite.Close();
            }
            return spReturn;
        }
        public static bool RemoveUser(string strLoginName, string strSiteURL)
        {
            SPSite spSite = null;
            SPWeb spWeb = null;
            try
            {
                spSite = new SPSite(strSiteURL);
                spWeb = spSite.OpenWeb();
                //this need use Site Users
                SPUserCollection col = spWeb.SiteUsers;
                SPUser user = col[strLoginName];
                if (user != null)
                    col.Remove(strLoginName);
            }
            catch (Exception)
            { }
            finally
            {
                spWeb.Close();
                spSite.Close();
            }
            return true;
        }