烦了我几天的代码终于完成了。

一直没有心情写，今天终于耐着性子写完了。
居然一次通过。Happy。

using System;
using System.Data;
using System.Data.OleDb;
using System.Collections;
using System.Collections.Generic;
using System.Text;

namespace DBUtil {
    /**//// <summary>
    /// 数据库里面的“种类”表的封装。
    /// 这类表的特征是只有两列，一列表示种类的名称(Name)，另外一列表示种类的ID(ID)。
    /// 表名需要命名为“*Enum”格式。
    /// </summary>
    sealed class EnumEntry /**//*: IEnumerable*/ {
        Singleton#region Singleton

        Static Register#region Static Register
        private static Dictionary<string, EnumEntry> _Reg = new Dictionary<string, EnumEntry>();
        private static EnumEntry Regist(string s, EnumEntry ee) {
            _Reg[s] = ee;
            return ee;
        }
        private static EnumEntry GetRegisted(string s) {
            if(_Reg.ContainsKey(s)) {
                return _Reg[s];
            }
            else {
                return null;
            }
        }
        #endregion

        public static EnumEntry GetInstance(string s) {
            EnumEntry ee = GetRegisted(s);
            if(ee == null) {
                return Regist(s, new EnumEntry(s));
            }
            else {
                return ee;
            }
        }
        #endregion

        Load from database to construct#region Load from database to construct
        private EnumEntry(string s) {
            _prefix = s;
            Load();
        }

        private string _SelectSQL = @"Select Name From {0} Order By ID ASC";
        private void Load() {
            _SelectSQL = String.Format(_SelectSQL, _prefix + "Enum");
            OleDbCommand comm = new OleDbCommand(_SelectSQL, _myConn.conn);
            _myConn.conn.Open();
            OleDbDataReader reader = comm.ExecuteReader();
            while(reader.Read()) {
                _enums.Add(reader.GetString(0));
            }
            reader.Close();
            _myConn.conn.Close();
        }
        #endregion

        Add a enum type#region Add a enum type
        private string _InsertSQL = @"Insert Into {0}
                                        Values (?, ?)";
        public void Add(string Name) {
            if(_enums.IndexOf(Name) != -1) {
                throw new Exception("Same name cannot be input twice!");
            }
            _InsertSQL = String.Format(_InsertSQL, _prefix + "Enum");
            int ID = _enums.Count - 1;
            //Add in object model
            _enums.Add(Name);
            //Add in database
            IDbCommand comm = new OleDbCommand(_InsertSQL, _myConn.conn);
            comm.Parameters.Add(new OleDbParameter("ID", ID));
            comm.Parameters.Add(new OleDbParameter("Name", Name));
            _myConn.conn.Open();
            comm.ExecuteNonQuery();
            _myConn.conn.Close();
        }
        #endregion

        Remove a enum type#region Remove a enum type
        private string _UpdateSQL = @"Update {0}
                                                Set ID = ?
                                                Where ID = ?";
        private string _DeleteSQLName = @"Delete From {0} Where Name = ?";
        public void Remove(string Name) {
            if(_enums.IndexOf(Name) == -1) {
                throw new Exception("There's no such name!");
            }
            _DeleteSQLName = String.Format(_DeleteSQLName, _prefix + "Enum");
            _UpdateSQL = String.Format(_UpdateSQL, _prefix + "Enum");
            int StartID = _enums.IndexOf(Name);
            int cnt = _enums.Count - StartID - 1;
            //Delete from object model
            _enums.Remove(Name);
            //Delete from database
            IDbCommand comm = new OleDbCommand(_DeleteSQLName, _myConn.conn);
            comm.Parameters.Add(new OleDbParameter("Name", Name));
            _myConn.conn.Open();
            comm.ExecuteNonQuery();
            _myConn.conn.Close();
            while(cnt != 0) {
                IDbCommand commup = new OleDbCommand(_UpdateSQL, _myConn.conn);
                commup.Parameters.Add(new OleDbParameter("ID", StartID));
                commup.Parameters.Add(new OleDbParameter("ID", StartID + 1));
                _myConn.conn.Open();
                commup.ExecuteNonQuery();
                _myConn.conn.Close();
                cnt--;
                StartID++;
            }
        }
        private string _DeleteSQLID = @"Delete From {0} Where ID = ?";
        public void Remove(int ID) {
            if(ID < 0 || ID >= _enums.Count) {
                throw new Exception("There's no such ID!");
            }
            _DeleteSQLID = String.Format(_DeleteSQLID, _prefix + "Enum");
            _UpdateSQL = String.Format(_UpdateSQL, _prefix + "Enum");
            int cnt = _enums.Count - ID - 1;
            //Delete from object model
            _enums.RemoveAt(ID);
            //Delete from database
            IDbCommand comm = new OleDbCommand(_DeleteSQLID, _myConn.conn);
            comm.Parameters.Add(new OleDbParameter("ID", ID));
            _myConn.conn.Open();
            comm.ExecuteNonQuery();
            _myConn.conn.Close();
            while(cnt != 0) {
                IDbCommand commup = new OleDbCommand(_UpdateSQL, _myConn.conn);
                commup.Parameters.Add(new OleDbParameter("ID", ID));
                commup.Parameters.Add(new OleDbParameter("ID", ID + 1));
                _myConn.conn.Open();
                commup.ExecuteNonQuery();
                _myConn.conn.Close();
                cnt--;
                ID++;
            }
        }
        #endregion

        public string this[int i] {
            get {
                return _enums[i];
            }
            set {
                _enums[i] = value;
            }
        }

        public int this[string name] {
            get {
                return _enums.IndexOf(name);
            }
        }

        public int Count {
            get {
                return _enums.Count;
            }
        }

        IEnumerable Members#region IEnumerable Members

        //public IEnumerator GetEnumerator() {
        //    return _enums.GetEnumerator();
        //}

        #endregion

        private List<string> _enums = new List<string>();
        private string _prefix = null;
        private MyConn _myConn = MyConn.GetInstance();
    }
}