菜鸟多线程问题

这个类在多线程中或者在asp.net中会报错吗 我菜鸟 多线程对我来说是无底洞
    public class StateManager
    {
        private static List<StateEntity> state = new List<StateEntity>();        public static StateEntity Oper(StateOper so, object Par)
        {
            return new StateManager().Opers(so, Par);
        }
        public StateEntity Opers(StateOper so, object par)
        {
            lock (this)
            {
                if (so == StateOper.Add)
                {
                    state.Add((StateEntity)par);
                }
                else if (so == StateOper.Del)
                {
                    state.RemoveAt((int)par);
                }
                else if (so == StateOper.Sel)
                {
                    for (int i = 0; i < state.Count; i++)
                    {
                        if (state[i].UserKey == ((StateEntity)par).UserKey)
                        {
                            return state[i];
                        }
                    }
                }
                else if(so==StateOper.Upd)
                {
                    for (int i = 0; i < state.Count; i++)
                    {
                        if (state[i].UserId == ((StateEntity)par).UserId)
                        {
                            state[i].LastTime = ((StateEntity)par).LastTime;
                        }
                    }
                }
            }
            return null;
        }
       
    }    public enum StateOper
    {
        Add,
        Del,
        Sel,
        Upd
    }