请教一个C# Linq 排序的问题（自定义排序）

各路大深，请教一个C# Linq 排序的问题，

我有个实体类是Class : User
里面有个属性是


    public class User
    {
        public string UName { get; set; }
        public int UAge { get; set; }
        public string ItemType { get; set; }
    }
大概有四种字符类型：   Active ,  Working  , Plan , PlanSub  

如果我按照普通方法排序
 List<User> userList = new List<User>();
            User u1 = new User { UName = "Tom", UAge = 9, ItemType = "active" };
            User u2 = new User { UName = "mary", UAge = 9, ItemType = "working" };
            User u3 = new User { UName = "jack", UAge = 9, ItemType = "active" };
            User u4 = new User { UName = "lee", UAge = 9, ItemType = "Plan" };
            User u5 = new User { UName = "Hua", UAge = 9, ItemType = "active" };
            User u6 = new User { UName = "Joph", UAge = 9, ItemType = "PlanSub" };

            userList.OrderBy(x => x.ItemType);

那么得到的顺序是  Active ,  Plan , PlanSub  ，Working   
这个order是根据字母顺序来排列的，也就是最普通的排序。

不过，现在用户想要特别排序 : Working , Active ,  Plan , PlanSub  
字母W 排在最前面 ， A排在中间 ， P放在最后。