十幾年前的系統(tǒng)中存在一個(gè)核心字典表，對(duì)此核心字典表的操作分散到不同的代碼模塊中，
而且沒有做代碼復(fù)用，都是在各自的模塊里直接操作DataTable
大體需求：

image.png

原系統(tǒng)代碼如下（實(shí)現(xiàn)依次檢查名字或者別名是否存在的需求，將查找到的數(shù)據(jù)創(chuàng)建一個(gè)新的DataTable供外部使用），不要問為啥這樣寫，那是一個(gè)沒有Linq，不懂模式的時(shí)代，

        if (s_Arry_ToValidate.Length > 0)
        {
            DataRow[] o_RowExist;
            DataRow o_RowItem;           
            string s_Item_Now = string.Empty;
            foreach (string s_Item in s_Arry_ToValidate)
            {

                s_Item_Now = s_Item.ToUpper().Trim();
                o_RowNew = o_DataTable_Columns.NewRow();

                o_RowExist = o_DataTable.Select("NAME='" + s_Item_Now + "'");
                if (o_RowExist.Length > 0)
                {
                    o_RowItem = o_RowExist[0];

                    o_RowNew[0] = o_RowItem[0];
                    o_RowNew[1] = o_RowItem[1].ToString();
                    o_RowNew[2] = o_RowItem[6];
                    o_RowNew[3] = o_RowItem[7];

                    o_DataTable_Columns.Rows.Add(o_RowNew);
                    continue;
                }

                o_RowExist = o_DataTable.Select("ALIAS_NAME1='" + s_Item_Now + "'");
                if (o_RowExist.Length > 0)
                {
                    o_RowItem = o_RowExist[0];

                    o_RowNew[0] = o_RowItem[0];
                    o_RowNew[1] = o_RowItem[1].ToString();
                    o_RowNew[2] = o_RowItem[6];
                    o_RowNew[3] = o_RowItem[7];

                    o_DataTable_Columns.Rows.Add(o_RowNew);
                    continue;
                }

                o_RowExist = o_DataTable.Select("ALIAS_NAME2='" + s_Item_Now + "'");
                if (o_RowExist.Length > 0)
                {
                    o_RowItem = o_RowExist[0];

                    o_RowNew[0] = o_RowItem[0];
                    o_RowNew[1] = o_RowItem[1].ToString();
                    o_RowNew[2] = o_RowItem[6];
                    o_RowNew[3] = o_RowItem[7];

                    o_DataTable_Columns.Rows.Add(o_RowNew);
                    continue;
                }

                o_RowExist = o_DataTable.Select("ALIAS_NAME3='" + s_Item_Now + "'");
                if (o_RowExist.Length > 0)
                {
                    o_RowItem = o_RowExist[0];

                    o_RowNew[0] = o_RowItem[0];
                    o_RowNew[1] = o_RowItem[1].ToString();
                    o_RowNew[2] = o_RowItem[6];
                    o_RowNew[3] = o_RowItem[7];

                    o_DataTable_Columns.Rows.Add(o_RowNew);
                    continue;
                }

                o_RowExist = o_DataTable.Select("ALIAS_NAME4='" + s_Item_Now + "'");
                if (o_RowExist.Length > 0)
                {
                    o_RowItem = o_RowExist[0];

                    o_RowNew[0] = o_RowItem[0];
                    o_RowNew[1] = o_RowItem[1].ToString();
                    o_RowNew[2] = o_RowItem[6];
                    o_RowNew[3] = o_RowItem[7];

                    o_DataTable_Columns.Rows.Add(o_RowNew);
                    continue;
                }

                o_RowExist = o_DataTable.Select("ALIAS_NAME5='" + s_Item_Now + "'");
                if (o_RowExist.Length > 0)
                {
                    o_RowItem = o_RowExist[0];

                    o_RowNew[0] = o_RowItem[0];
                    o_RowNew[1] = o_RowItem[1].ToString();
                    o_RowNew[2] = o_RowItem[6];
                    o_RowNew[3] = o_RowItem[7];

                    o_DataTable_Columns.Rows.Add(o_RowNew);
                    continue;
                }

            }

        }

重構(gòu)

這里面就有一個(gè)職責(zé)鏈的需求，先判斷英文名字，存在了則返回?cái)?shù)據(jù)，不存在則在各個(gè)別名中查找，因?yàn)榇讼到y(tǒng)大部分的查找的是英文名字，所以要放到鏈的第一個(gè)。
假設(shè)有如下數(shù)據(jù)：

image.png

代碼：

 interface ICheckHandler
    {
        DataRow Process(EnumerableRowCollection<DataRow> allData, string name2Check);
    }

    class NameCheckHandler : ICheckHandler
    {
        public DataRow Process(EnumerableRowCollection<DataRow> allData, string name2Check)
        {
            var resuslt = allData.Where(item => item["NAME"].ToString().Equals(name2Check));
            if (resuslt.Any())
            {
                return resuslt.FirstOrDefault();
            }
            return null;
        }
    }

    class ALIASName1CheckHandler : ICheckHandler
    {
        public DataRow Process(EnumerableRowCollection<DataRow> allData, string name2Check)
        {
            var resuslt = allData.Where(item => item["ALIAS_NAME1"].ToString().Equals(name2Check));
            if (resuslt.Any())
            {
                return resuslt.FirstOrDefault();
            }
            return null;
        }
    }

    class ALIASName2CheckHandler : ICheckHandler
    {
        public DataRow Process(EnumerableRowCollection<DataRow> allData, string name2Check)
        {
            var resuslt = allData.Where(item => item["ALIAS_NAME2"].ToString().Equals(name2Check));
            if (resuslt.Any())
            {
                return resuslt.FirstOrDefault();
            }
            return null;
        }
    }


    class NameCheckChain
    {
        private List<ICheckHandler> handlers = new List<ICheckHandler>();
        public void AddHandler(ICheckHandler handler)
        {
            handlers.Add(handler);
        }
        public DataRow Process(DataTable allData, string name2Check)
        {
            foreach (var handler in handlers)
            {
                DataRow result = handler.Process(allData.AsEnumerable(), name2Check);
                if (result != null)
                {
                    return result;
                }
            }
            return null;
        }
    }


    class Program
    {
        static void Main(string[] args)
        {
            string[] names = { "機(jī)匣振動(dòng)03", "機(jī)振05", "jxzd_01" };
            List<DataRow> rows1 = GetDetails(names);
            foreach (var row in rows1)
            {
                Console.WriteLine(string.Join(",", row.ItemArray));
            }
            //List<DataRow> rows2 = GetDetails2(names);
        }

        #region 根據(jù)任意名字找信息

        //隨意輸入一個(gè)名稱，或者別名1...別名n,找到此CHANNEL的詳細(xì)定義
        static List<DataRow> GetDetails(string[] names)
        {
            NameCheckChain nc = new NameCheckChain();
            nc.AddHandler(new NameCheckHandler());
            nc.AddHandler(new ALIASName1CheckHandler());
            nc.AddHandler(new ALIASName2CheckHandler());

            List<DataRow> result = new List<DataRow>();
            DataTable dt = GetAllDatas();
            foreach (string name in names)
            {
                var row = nc.Process(dt, name);
                if (row != null)
                {
                    result.Add(row);
                }
            }
            return result;
        }

        static List<DataRow> GetDetails2(string[] names)
        {
            var handlers = new List<Func<EnumerableRowCollection<DataRow>, string, DataRow>>();
            handlers.Add((new NameCheckHandler()).Process);
            handlers.Add((new ALIASName1CheckHandler()).Process);
            handlers.Add((new ALIASName2CheckHandler()).Process);

            List<DataRow> result = new List<DataRow>();
            var dt = GetAllDatas().AsEnumerable();
            foreach (string name in names)
            {
                foreach (var handler in handlers)
                {
                    var row = handler(dt, name);
                    if (row != null)
                    {
                        result.Add(row);
                        break;
                    }
                }
            }
            return result;
        }

        static DataTable GetAllDatas()
        {
            DataHelper dh = new DataHelper();
            string sql = @"SELECT ID,NAME,ALIAS_NAME1,ALIAS_NAME2,ALIAS_NAME3,ALIAS_NAME4 FROM 表名"; //空字符串的名字也要保留，因?yàn)閯e名保存的位置隨機(jī)
            dh.CreateCommand(sql);
            return dh.selectExecute();
        }


        #endregion

        #region 數(shù)據(jù)導(dǎo)入相關(guān)
        static void DataImport()
        {
            DataTable data2Import = CSVHelper.ReadFromCSV(@"D:\ImportTemplate.csv", true);
            CheckExistData(data2Import);
            Insert2DB(data2Import);
        }

。。。。。。

以上的實(shí)現(xiàn)中，并么有在ICheckHandler的實(shí)現(xiàn)類中定義下一個(gè)實(shí)現(xiàn)了ICheckHandler的鏈，而是通過List<ICheckHandler> handlers的方式實(shí)現(xiàn)了鏈的概念。
在GetDetails2方法中，更是將ICheckHandler的接口舍棄，直接定義了 方法鏈進(jìn)行測試。
這里的重構(gòu)也只是思考職責(zé)鏈的表現(xiàn)形式和實(shí)際的應(yīng)用。
如果各個(gè)別名還有更復(fù)雜的需求，定義ICheckHandler接口肯定是最好的辦法。

  public class DataHelper
    {
        private MySqlConnection conn = null;
        private MySqlCommand command = null;
        private MySqlDataReader reader = null;

        /// <summary>
        /// 構(gòu)造方法里建議連接
        /// </summary>
        /// <param name="connstr"></param>
        public DataHelper(string connstr)
        {
            //我這里是在構(gòu)造函數(shù)里傳入mysql連接語句
            conn = new MySqlConnection(connstr);
        }

        public DataHelper()
        {
            string mysqlStr = "Data Source=127.0.0.1;User Id=root;Password=;;pooling=false;CharSet=utf8;port=3306;Database=test;";
            conn = new MySqlConnection(mysqlStr);
        }
        /// <summary>
        /// 發(fā)送指令
        /// </summary>
        /// <param name="sql"></param>
        public void CreateCommand(string sql)
        {
            conn.Open();
            command = new MySqlCommand(sql, conn);
        }
        /// <summary>
        /// 增、刪、改公共方法
        /// </summary>
        /// <returns></returns>
        public int commonExecute()
        {
            int res = -1;
            try
            {
                res = command.ExecuteNonQuery();
            }
            catch (MySqlException ex)
            {
                Console.WriteLine("操作失敗!" + ex.Message);
            }
            conn.Close();
            return res;
        }
        /// <summary>
        /// 查詢方法
        /// 注意：盡量不要用select * from table表（返回的數(shù)據(jù)過長時(shí)，DataTable可能會(huì)出錯(cuò)），最好指定要查詢的字段。
        /// </summary>
        /// <returns></returns>
        public DataTable selectExecute()
        {
            DataTable dt = new DataTable();
            using (reader = command.ExecuteReader(CommandBehavior.CloseConnection))
            {
                dt.Load(reader);
            }
            return dt;
        }

    }


 public class CSVHelper
    {
        public static DataTable ReadFromCSV(string path, bool hasTitle = false)
        {
            DataTable dt = new DataTable();           //要輸出的數(shù)據(jù)表
            StreamReader sr = new StreamReader(path); //文件讀入流
            bool bFirst = true;                       //指示是否第一次讀取數(shù)據(jù)

            //逐行讀取
            string line;
            while ((line = sr.ReadLine()) != null)
            {
                string[] elements = line.Split(',');

                //第一次讀取數(shù)據(jù)時(shí)，要?jiǎng)?chuàng)建數(shù)據(jù)列
                if (bFirst)
                {
                    for (int i = 0; i < elements.Length; i++)
                    {
                        dt.Columns.Add();
                    }
                    bFirst = false;
                }

                //有標(biāo)題行時(shí)，第一行當(dāng)做標(biāo)題行處理
                if (hasTitle)
                {
                    for (int i = 0; i < dt.Columns.Count && i < elements.Length; i++)
                    {
                        dt.Columns[i].ColumnName = elements[i];
                    }
                    hasTitle = false;
                }
                else //讀取一行數(shù)據(jù)
                {
                    if (elements.Length == dt.Columns.Count)
                    {
                        dt.Rows.Add(elements);
                    }
                    else
                    {
                        //throw new Exception("CSV格式錯(cuò)誤：表格各行列數(shù)不一致");
                    }
                }
            }
            sr.Close();

            return dt;
        }

        /// <summary>
        /// 將DataTable內(nèi)容保存到CSV文件中
        /// </summary>
        /// <param name="dt">數(shù)據(jù)表</param>
        /// <param name="path">CSV文件地址</param>
        /// <param name="hasTitle">是否要輸出數(shù)據(jù)表各列列名作為CSV文件第一行</param>
        public static void SaveToCSV(DataTable dt, string path, bool hasTitle = false)
        {
            StreamWriter sw = new StreamWriter(path);

            //輸出標(biāo)題行（如果有）
            if (hasTitle)
            {
                for (int i = 0; i < dt.Columns.Count; i++)
                {
                    sw.Write(dt.Columns[i].ColumnName);
                    if (i != dt.Columns.Count - 1)
                    {
                        sw.Write(",");
                    }
                }
                sw.WriteLine();
            }

            //輸出文件內(nèi)容
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    sw.Write(dt.Rows[i][j].ToString());
                    if (j != dt.Columns.Count - 1)
                    {
                        sw.Write(",");
                    }
                }
                sw.WriteLine();
            }

            sw.Close();

        }
    }