实战分层架构

现在可选的框架

    现在我们开发一个.net应用，面临的选择比较多。我们可以选择entity framework, enterprise library, nhibernate, 还有一个mybatis.net, 即java世界mybatis/ibatis的.net版。 IOC的框架可以选择Unity, Ninject，Spring.net(java的spring对应的.net版本)。Entity framework可以使用linq查询，有好几种开发模式，如code first, db first, 可以不用写sql。Entity framework适合sql server。虽有mysql提供了entity framework的provider，但是不是很好, 经常不得不单独写sql来操作mysql. Enterprise library是个不错的选择，有log, exception, policy injection的一些东西，操作数据库也比较好。nhibernate是java版hibernate的.net对应版本。对数据库包装得比较多，可以不用写sql. 但是有些时候对数据库操作不够优化，会有一些多余数据库操作。带来一些性能的影响。mybatis.net是个介于ado.net与nhibernate之间的框架，它负责数据库对象与内存对象的映射。程序员必须写sql语句来操作数据库。IOC的框架中Unity, Ninject, Spring.net, 都是不错的框架。有时这些框架能照顾到我们大部分的需求，也有一些情况，不能全部照顾到我们的需求。这时就得用一些老办法。比如直接就用ado.net

适应多种数据库的db helper代码

    这里主要是想说一些基于ado.net来开发asp.net mvc应用的一些思路。为什么选用ado.net呢，ado.net性能可以达到最好，灵活。先看一段db helper的代码:

using System;
using System.Configuration;
using System.Data;
using System.Data.Common;
using System.Collections.Generic;

namespace DataAccessCommon
{
    /// <summary>
    /// The MyDBHelper class is intended to encapsulate high performance, scalable best practices for 
    /// common uses of SqlClient, OracleClient, OleDb, and others
    /// </summary>
    public static class MyStaticDBHelper
    {
        public struct MyDBParameter
        {
            public string strParameterName;
            public DbType dbType;
            public object value;
            public ParameterDirection parameterDirection;

            public MyDBParameter(string parameterName, DbType type, object theValue, ParameterDirection direction = ParameterDirection.Input)
            {
                strParameterName = parameterName;
                dbType = type;
                value = theValue;
                parameterDirection = direction;
            }
        }
        public static string DatabaseType = "SqlServer";
        private static Dictionary<string, string> providers = new Dictionary<string, string>() {
        { "SqlServer", "System.Data.SqlClient" }
        , { "Oracle", "System.Data.OracleClient" }
        , { "OleDb", "System.Data.OleDb" } 
        };
        private static DbProviderFactory dataFactory = DbProviderFactories.GetFactory(providers[DatabaseType]);
        public static string CONNECTION_STRING = ConfigurationManager.AppSettings["ConnectionString"];

        #region private methods
        private static void AttachParameters(DbCommand command, DbParameter[] parameters)
        {
            if (parameters != null)
            {
                command.Parameters.AddRange(parameters);
            }
        }

        private static DbCommand CreateCommand(object conn)
        {
            DbCommand command = null;
            //If it is just a connection(not a transaction)
            if (conn is DbConnection)
            {
                command = ((DbConnection)conn).CreateCommand();
                if (command.Connection.State != ConnectionState.Open)
                {
                    command.Connection.Open();
                }
            }
            else //It is a transaction, then join the transaction
            {
                command = ((DbTransaction)conn).Connection.CreateCommand();
                command.Transaction = (DbTransaction)conn;
            }
            return command;
        }

        private static DbCommand SetupCommand(object conn, CommandType commandType, string strSQLOrSPName, List<MyDBParameter> myDBParameters)
        {
            DbParameter[] parameters = myDBParameters != null ? CreateDBParameters(myDBParameters).ToArray() : null;
            DbCommand command = CreateCommand(conn);
            command.CommandText = strSQLOrSPName;
            command.CommandType = commandType;
            AttachParameters(command, parameters);
            return command;
        }

        private static DbParameter CreateDBParameter(string strParameterName, DbType dbType, object value, ParameterDirection direction)
        {
            DbParameter parameter = dataFactory.CreateParameter();
            parameter.ParameterName = strParameterName;
            parameter.DbType = dbType;
            parameter.Value = value;
            parameter.Direction = direction;
            return parameter;
        }

        private static List<DbParameter> CreateDBParameters(List<MyDBParameter> myDBParameters)
        {
            List<DbParameter> parameters = new List<DbParameter>();
            foreach (MyDBParameter myDBParameter in myDBParameters)
            {
                parameters.Add(CreateDBParameter(myDBParameter.strParameterName, myDBParameter.dbType, myDBParameter.value, myDBParameter.parameterDirection));
            }
            return parameters;
        }
        #endregion

        public static DbConnection GetConnection()
        {
            DbConnection connection = dataFactory.CreateConnection();
            connection.ConnectionString = CONNECTION_STRING;
            return connection;
        }

        public static int ExecuteNonQuery(object conn, CommandType commandType, string strSQLOrSPName, List<MyDBParameter> myDBParameters = null)
        {
            DbCommand command = SetupCommand(conn, commandType, strSQLOrSPName, myDBParameters);
            return command.ExecuteNonQuery();
        }

        public static DataSet ExecuteDataset(object conn, CommandType commandType, string strSQLOrSPName, List<MyDBParameter> myDBParameters = null)
        {
            DbCommand command = SetupCommand(conn, commandType, strSQLOrSPName, myDBParameters);
            DbDataAdapter dataAdaptor = dataFactory.CreateDataAdapter();
            DataSet ds = new DataSet();
            dataAdaptor.SelectCommand = command;
            dataAdaptor.Fill(ds);
            return ds;
        }

        public static DbDataReader ExecuteReader(object conn, CommandType commandType, string strSQLOrSPName, List<MyDBParameter> myDBParameters = null)
        {
            DbCommand command = SetupCommand(conn, commandType, strSQLOrSPName, myDBParameters);
            return command.ExecuteReader();
        }

        public static object ExecuteScalar(object conn, CommandType commandType, string strSQLOrSPName, List<MyDBParameter> myDBParameters = null)
        {
            DbCommand command = SetupCommand(conn, commandType, strSQLOrSPName, myDBParameters);
            return command.ExecuteScalar();
        }
    }
}

此代码能支持访问Oracle, sql server, OleDB。用的都是DbConnection之类的。只要开始选择了正确的provider, DbProviderFactories就给创建相应的connection, command等类，就可以顺利地处理这个对应的数据库了。sql的参数是DbType。用来适应数据库类型。MyDBParameter结构封装了参数名，类型，参数值，传入传出方向。目前的版本只考虑了一个数据库连接。连接串只有一个。DbProviderFactory只有一个实例。没有考虑到动态切换连接的情况。如果是要多个连接，得要多个DbProviderFactory的实例。CreateCommand方法里判断了传入的的数据库连接是一个DbConnection还是一个DbTransaction，如果是一个DbTransaction的话，可以加入这个数据库事务。如果只是一个DbConnection则不加入已有的数据库事务，使用自动的数据库事务。

数据实体类

using System;
using System.Collections.Generic;

namespace DataEntity
{
    public class UserMenuItem
    {
        #region Properties
        public int MenuItemID { get; set; }
        public string MenuItemName { get; set; }
        public int MenuID { get; set; }
        public int Ordinal { get; set; }
        public int Indent { get; set; }
        #endregion
    }
}

纯数据的类。这里使用了比较老的c#语法。也可以加上DataAnnotation的标签。可以实现验证数据，也可以加上Display标签，引用资源文件。这个数据实体类在MVC页面里绑定时可以显示想应的label。label的内容来自于资源文件，便于使用多语言的界面。

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using Resource.Entity;

namespace DataEntity
{
    public class UserAccount
    {
        #region Properties
        public int ID { get; set; }

        [Required(ErrorMessageResourceType=typeof(Resource.Entity.UserAccount), ErrorMessageResourceName="Common_Required_ErrorMessage")]
        [StringLength(30, ErrorMessageResourceType=typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "NAME_StringLength_ErrorMessage")]
        [RegularExpression(@"[a-zA-Z].*", ErrorMessageResourceType=typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "NAME_RegularExpression_ErrorMessage")]
        [Display(ResourceType=typeof(Resource.Entity.UserAccount), Name="NAME_DisplayName")]
        public string Name { get; set; }

        [Required(ErrorMessageResourceType=typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "Common_Required_ErrorMessage")]
        [RegularExpression(@"[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?"
            , ErrorMessageResourceType=typeof(Resource.Entity.UserAccount), ErrorMessageResourceName="EMAIL_RegularExpression_ErrorMessage")]
        [Display(ResourceType=typeof(Resource.Entity.UserAccount), Name="EMAIL_DisplayName")]
        public string Email { get; set; }

        [Display(ResourceType = typeof(Resource.Entity.UserAccount), Name = "PASSWORD_DisplayName")]
        [Required(ErrorMessageResourceType = typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "Common_Required_ErrorMessage")]
        [StringLength(32, ErrorMessageResourceType = typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "PASSWORD_StringLength", MinimumLength = 8)]
        public string Password { get; set; }

        [Display(ResourceType = typeof(Resource.Entity.UserAccount), Name = "Balance")]
        public decimal Balance { get; set; }

        [Required(ErrorMessageResourceType = typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "Common_Required_ErrorMessage")]
        [Display(ResourceType = typeof(Resource.Entity.UserAccount), Name = "CONFIRMPASSWORD_DisplayName")]
        [Compare("Password", ErrorMessageResourceType = typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "CONFIRMPASSWORD_CompareErrorMessage")]
        public string ConfirmPassword { get; set; }

        [Required(ErrorMessageResourceType = typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "Common_Required_ErrorMessage")]
        [Display(ResourceType = typeof(Resource.Entity.UserAccount), Name = "OLDNAME_DisplayName")]
        public string OldName { get; set; }

        [Required(ErrorMessageResourceType = typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "Common_Required_ErrorMessage")]
        [Display(ResourceType = typeof(Resource.Entity.UserAccount), Name = "OLDEMAIL_DisplayName")]
        public string OldEmail { get; set; }

        [Required(ErrorMessageResourceType = typeof(Resource.Entity.UserAccount), ErrorMessageResourceName = "Common_Required_ErrorMessage")]
        [Display(ResourceType = typeof(Resource.Entity.UserAccount), Name = "OLDPassword_DisplayName")]
        public string OldPassword { get; set; }
        #endregion
    }
}

下面是数据访问的代码:

using System;
using System.Collections.Generic;
using System.Data;
using DataEntity;
using DataAccessCommon;

namespace DataAccess
{
    public class DALUserMenuItem
    {
        #region data access methods

        public int DeleteUserMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuItemID", DbType.Int32, usermenuitem.MENUITEMID)
            };

            string strSQL = "DELETE FROM [UserMenuItem]   WHERE   [MenuItemID] = @MenuItemID";

            int result = 0;
            result = MyStaticDBHelper.ExecuteNonQuery(conn, System.Data.CommandType.Text, strSQL, paras);
            return result;

        }

        public int UpdateUserMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuItemName", DbType.String, usermenuitem.MENUITEMNAME),
                new MyStaticDBHelper.MyDBParameter("@MenuID", DbType.Int32, usermenuitem.MENUID),
                new MyStaticDBHelper.MyDBParameter("@Ordinal", DbType.Int32, usermenuitem.ORDINAL),
                new MyStaticDBHelper.MyDBParameter("@MenuItemID", DbType.Int32, usermenuitem.MENUITEMID)
            };

            string strSQL = "UPDATE [UserMenuItem] SET   [MenuItemName] = @MenuItemName,  [MenuID] = @MenuID,  [Ordinal] = @Ordinal  WHERE   [MenuItemID] = @MenuItemID";

            int result = 0;
            result = MyStaticDBHelper.ExecuteNonQuery(conn, System.Data.CommandType.Text, strSQL, paras);
            return result;

        }

        public int AddUserMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuItemName", DbType.String, usermenuitem.MENUITEMNAME),
                new MyStaticDBHelper.MyDBParameter("@MenuID", DbType.Int32, usermenuitem.MENUID),
                new MyStaticDBHelper.MyDBParameter("@Ordinal", DbType.Int32, usermenuitem.ORDINAL),
                new MyStaticDBHelper.MyDBParameter("@MenuItemID", DbType.Int32, usermenuitem.MENUITEMID)
            };

            string strSQL = "INSERT INTO [UserMenuItem] (  [MenuItemName] ,  [MenuID] ,  [Ordinal]  ) VALUES( @MenuItemName, @MenuID, @Ordinal );  SELECT SCOPE_IDENTITY() as [MenuItemID]";

            int result = 0;
            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL, paras);
            if (ds.Tables.Count > 0 && ds.Tables[0].Rows.Count > 0){
                usermenuitem.MENUITEMID = Convert.ToInt32(ds.Tables[0].Rows[0][0]);
                result = 1;
            }
            return result;

        }

        public List<UserMenuItem> GetAllUserMenuItem(Object conn)
        {

            string strSQL = "SELECT * FROM [UserMenuItem] ";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL);

            return DataMapper.MapDataTableToObjectList<UserMenuItem>(ds.Tables[0]);

        }

        public UserMenuItem FindAUserMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuItemID", DbType.Int32, usermenuitem.MENUITEMID)
            };

            string strSQL = "SELECT * FROM [UserMenuItem]   WHERE   [MenuItemID] = @MenuItemID";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL, paras);

            return DataMapper.MapDataTableToSingleRow<UserMenuItem>(ds.Tables[0]);

        }

        public System.Int32 SelectCountUserMenuItem(Object conn)
        {

            string strSQL = "SELECT COUNT(1) AS Count FROM [UserMenuItem] ";

            Object obj = null;
            obj = MyStaticDBHelper.ExecuteScalar(conn, System.Data.CommandType.Text, strSQL);
            return (System.Int32)obj;

        }

        public System.Int32 SelectCountWhereClauseUserMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuItemID", DbType.Int32, usermenuitem.MENUITEMID)
            };

            string strSQL = "SELECT COUNT(1) AS Count FROM [UserMenuItem]   WHERE   [MenuItemID] = @MenuItemID";

            Object obj = null;
            obj = MyStaticDBHelper.ExecuteScalar(conn, System.Data.CommandType.Text, strSQL, paras);
            return (System.Int32)obj;

        }

        public List<UserMenuItem> SelectTopUserMenuItem(Object conn)
        {

            string strSQL = "SELECT Top 50 *  FROM [UserMenuItem] ";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL);

            return DataMapper.MapDataTableToObjectList<UserMenuItem>(ds.Tables[0]);

        }

        public List<UserMenuItem> SelectOrderByPrimaryKeyUserMenuItem(Object conn)
        {

            string strSQL = "SELECT *  FROM [UserMenuItem] ORDER BY [MenuItemID] , [MenuItemName] , [MenuID] , [Ordinal]";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL);

            return DataMapper.MapDataTableToObjectList<UserMenuItem>(ds.Tables[0]);

        }

        public List<UserMenuItem> SelectGroupByPrimaryKeyUserMenuItem(Object conn)
        {

            string strSQL = "SELECT * FROM [UserMenuItem] GROUP BY [MenuItemID] , [MenuItemName] , [MenuID] , [Ordinal]";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL);

            return DataMapper.MapDataTableToObjectList<UserMenuItem>(ds.Tables[0]);

        }

        public List<UserMenuItem> SelectUserMenuItemsByMenuID(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuID", DbType.Int32, usermenuitem.MENUID)
            };
            
            string strSQL = "SELECT * FROM [UserMenuItem] WHERE [MenuID] = @MenuID ORDER BY [Ordinal]";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL, paras);

            return DataMapper.MapDataTableToObjectList<UserMenuItem>(ds.Tables[0]);
        }

        public UserMenuItem SelectPreviousMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuID", DbType.Int32, usermenuitem.MENUID),
                new MyStaticDBHelper.MyDBParameter("@Ordinal", DbType.Int32, usermenuitem.ORDINAL)
            };

            string strSQL = "SELECT TOP 1 * FROM [UserMenuItem] WHERE [MenuID] = @MenuID AND [Ordinal] < @Ordinal ORDER BY [Ordinal] DESC";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL, paras);

            return DataMapper.MapDataTableToSingleRow<UserMenuItem>(ds.Tables[0]);
        }

        public UserMenuItem SelectNextMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuID", DbType.Int32, usermenuitem.MENUID),
                new MyStaticDBHelper.MyDBParameter("@Ordinal", DbType.Int32, usermenuitem.ORDINAL)
            };

            string strSQL = "SELECT TOP 1 * FROM [UserMenuItem] WHERE [MenuID] = @MenuID AND [Ordinal] > @Ordinal ORDER BY [Ordinal] ASC";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL, paras);

            return DataMapper.MapDataTableToSingleRow<UserMenuItem>(ds.Tables[0]);
        }

        public int MoveLeftMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuItemID", DbType.Int32, usermenuitem.MENUITEMID)
            };

            string strSQL = "UPDATE [UserMenuItem] SET [Indent] = CASE WHEN [Indent] - 1 >= 0 THEN [Indent] - 1 ELSE 0 END WHERE [MenuItemID] = @MenuItemID";

            int iResult = 0;
            iResult = MyStaticDBHelper.ExecuteNonQuery(conn, System.Data.CommandType.Text, strSQL, paras);

            return iResult;
        }

        public int MoveRightMenuItem(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuItemID", DbType.Int32, usermenuitem.MENUITEMID)
            };

            string strSQL = "UPDATE [UserMenuItem] SET [Indent] = CASE WHEN [Indent] + 1 <= 2 THEN [Indent] + 1 ELSE 2 END WHERE [MenuItemID] = @MenuItemID";

            int iResult = 0;
            iResult = MyStaticDBHelper.ExecuteNonQuery(conn, System.Data.CommandType.Text, strSQL, paras);

            return iResult;
        }

        public UserMenuItem SelectMaxOrdinal(Object conn, UserMenuItem usermenuitem)
        {
            List<MyStaticDBHelper.MyDBParameter> paras = new List<MyStaticDBHelper.MyDBParameter> {
                new MyStaticDBHelper.MyDBParameter("@MenuID", DbType.Int32, usermenuitem.MENUID)
            };

            string strSQL = "SELECT IsNull(Max(Ordinal),0) as Ordinal FROM [UserMenuItem] WHERE [MenuID] = @MenuID";

            DataSet ds = null;
            ds = MyStaticDBHelper.ExecuteDataset(conn, System.Data.CommandType.Text, strSQL, paras);

            return DataMapper.MapDataTableToSingleRow<UserMenuItem>(ds.Tables[0]);
        }
        #endregion
    }
}

这个数据访问的代码都是这种方式，开始准备参数。用的都是MyStaticDBHelper.MyDBParameter结构。给出参数名，参数类型，参数值和参数方向（输入还是输出）。然后就是一个sql语句，其中有参数。之后是根据查询的类型，update/delete/insert的就调用db helper的ExecuteNonQuery方法，如果是select一个表的话，调用db helper的ExecuteDataset方法。再之后，就要将返回的值给转换成对应的返回类型。如一个实体对象或者实体对象列表。这个类里的sql语句都是预先设计好的sql语句，每个sql语句都有参数，然后每个sql查询都有一个c#方法与之对应。DataMapper.MapDataTableToSingleRow是将DataTable中第一行转换成一个实体对象。DataMapper.MapDataTableToObjectList是将返回的DataTable转换成实体类的列表, 即List<实体类>，这里DataMapper类采用了Reflection的方式来进行转换实体类。虽然不是最快的。在某些情况下也可以接受。我们做过一个实例程序来对比，将DataTable转成实体类列表，有直接赋值，Emit, Reflection, delegate, Expression tree等不同的方法，经过性能测试，直接赋值是最快的。Emit稍微比直接赋值慢，但是已经很快了。直接赋值写代码比较繁琐。Emit的方法代码稍微有点复杂，但是运行效率不错。又比较灵活。是个相当好的方法，Emit和Expresssion Tree的方法有一些缺点，就是很难调试，万一出现问题会很难找到问题的根源。这里是比较不同方法将DataTable转成数据实体类的测试代码:  https://files.cnblogs.com/mikelij/testGenerateEntity.zip, 大家可以下载了去试试，应该说这几种方法都还不错。这里的代码选用了Reflection方法。因为Reflection也没有慢得很多。Reflection方法的兼容性好。不会出问题。Emit和Express tree方法经常会遇到不兼容类型的问题。而且很难排查问题。

 数据映射的类

using System;
using System.Data;
using System.Configuration;
using System.Collections.Generic;
using System.Reflection;

namespace DataAccessCommon
{
    public class DataMapper
    {

        public static List<TType> MapDataTableToObjectList<TType>(DataTable dt) where TType : new()
        {
            List<TType> result = new List<TType>();
            foreach (DataRow currentRow in dt.Rows)
            {
                TType ttype = new TType();
                for (int i = 0; i < dt.Columns.Count; i++)
                {
                    for (int j = 0; j < ttype.GetType().GetProperties().Length; j++)
                    {
                        if (dt.Columns[i].ColumnName.ToUpper() == ttype.GetType().GetProperties()[j].Name.ToUpper())
                        {
                            ttype.GetType().GetProperties()[j].SetValue(ttype, currentRow[i], null);
                            break;
                        }
                    }
                }
                result.Add(ttype);
                ttype = new TType();
            }
            return result;
        }

        public static TType MapDataTableToSingleRow<TType>(DataTable dt) where TType : new()
        {
            TType ttype = new TType();
            if (dt.Rows.Count > 0)
            {
                DataRow currentRow = dt.Rows[0];
                for (int i = 0; i < dt.Columns.Count; i++)
                {
                    for (int j = 0; j < ttype.GetType().GetProperties().Length; j++)
                    {
                        if (dt.Columns[i].ColumnName.ToUpper() == ttype.GetType().GetProperties()[j].Name.ToUpper())
                        {
                            ttype.GetType().GetProperties()[j].SetValue(ttype, currentRow[i], null);
                            break;
                        }
                    }
                }
            }
            return ttype;
        }
    }
}

商业类的代码

商业类的代码是基于我们OOA/OOD设计出的。比如一个银行ATM的例子，其业务里有若干名词，比如银行户头，ATM机等名词，每个名词下又有若干属性，比如银行帐号，帐号所有者名字，开立日期等，ATM机有ATM机号，地理位置，所属银行编号，等等。围绕着这些名词，有相关的一些动作。比如取钱，存钱，插卡入ATM机，记录ATM流水。等等等等。这里已经将名词的数据属性放到了数据实体类里。这些数据实体类里就只有那些名词的数据属性，没有那些动作，即一个纯数据的类。这里要提到的商业类包含了商业方法的类，这些商业方法就对应着那些动作。比如取钱，就有一个Withdraw方法对应。存钱就就一个Deposite方法对应。这两个方法都放在一个叫BankAccount的的商业类里面。这里用的银行的例子，说明这里所用到的设计方法。

使用Unity之类的IOC容器进行policy injection

下面就要说说IOC了，就是说我们设计一个商业类，里面有几个商业方法。如果让调用者直接依赖于这个商业类，那么将来有一天要改变这些商业方法时，可能就不得不同时改调用者和商业类。为了避免这种情况，我们可以从商业类提取出一个接口。这个接口只有这些动作的名字，没有具体具体实现。然后由负责具体实现的商业类来实现这些接口。说了这些东西与IOC有什么关系呢？这样做正是为了实现IOC打下基础。要知道象Unity这样的IOC容器，都是负责创建对象。它负责从接口映射到具体的商业类。当调用者需要创建一个接口的实例，接口本身是不能实例化的，容器会为调用者创建一个实现了该接口商业类的实例。

一个商业接口的例子：

using System;
namespace BusinessLogic
{
    [MyDBHandler]
    public interface IBLLUserMenu
    {
        int AddUserMenu(DataEntity.UserMenu usermenu);
        int DeleteUserMenu(DataEntity.UserMenu usermenu);
        DataEntity.UserMenu FindAUserMenu(DataEntity.UserMenu usermenu);
        System.Collections.Generic.List<DataEntity.UserMenu> GetAllUserMenu();
        int SelectCountUserMenu();
        int SelectCountWhereClauseUserMenu(DataEntity.UserMenu usermenu);
        System.Collections.Generic.List<DataEntity.UserMenu> SelectGroupByPrimaryKeyUserMenu();
        System.Collections.Generic.List<DataEntity.UserMenu> SelectMenusByApplicationID(DataEntity.UserMenu usermenu);
        System.Collections.Generic.List<DataEntity.UserMenu> SelectOrderByPrimaryKeyUserMenu();
        System.Collections.Generic.List<DataEntity.UserMenu> SelectTopUserMenu();
        int UpdateUserMenu(DataEntity.UserMenu usermenu);
        object CONNECTION { get; set; }
        DataEntity.UserMenu USERMENU { get; set; }
        System.Collections.Generic.List<DataEntity.UserMenu> USERMENU_LIST { get; set; }
    }
}

此代码中的MyDBHandler是一个字定义的attribute, 用于Unity来进行拦截判断。有这个attribute就拦截，没有就不拦截。
而相应的商业类就是这样的：

using System;
using System.Collections.Generic;
using System.Data;
using DataEntity;
using DataAccess;
using DataAccessCommon;
using CommonUtil;

namespace BusinessLogic
{
    internal class BLLUserMenu : BusinessLogic.IBLLUserMenu
    {
        private readonly DataAccess.DALUserMenu dal = new DataAccess.DALUserMenu();
        private object conn = null;
        private UserMenu usermenu;
        private List<UserMenu> usermenus;

        public object CONNECTION
        {
            get
            {
                return conn;
            }
            set
            {
                conn = value;
            }
        }
        
        public UserMenu USERMENU
        {
            get
            {
                return usermenu;
            }
            set
            {
                usermenu = value;
            }
        }
        
        public List<UserMenu> USERMENU_LIST
        {
            get
            {
                return usermenus;
            }
            set
            {
                usermenus = value;
            }
        }
        
        #region business logic method

        public int DeleteUserMenu(UserMenu usermenu)
        {
            return dal.DeleteUserMenu(conn,usermenu);
        }

        public int UpdateUserMenu(UserMenu usermenu)
        {
            return dal.UpdateUserMenu(conn,usermenu);
        }

        public int AddUserMenu(UserMenu usermenu)
        {
            return dal.AddUserMenu(conn,usermenu);
        }

        public List<UserMenu> GetAllUserMenu()
        {
            return dal.GetAllUserMenu(conn);
        }

        public UserMenu FindAUserMenu(UserMenu usermenu)
        {
            return dal.FindAUserMenu(conn,usermenu);
        }

        public System.Int32 SelectCountUserMenu()
        {
            return dal.SelectCountUserMenu(conn);
        }

        public System.Int32 SelectCountWhereClauseUserMenu(UserMenu usermenu)
        {
            return dal.SelectCountWhereClauseUserMenu(conn,usermenu);
        }

        public List<UserMenu> SelectTopUserMenu()
        {
            return dal.SelectTopUserMenu(conn);
        }

        public List<UserMenu> SelectOrderByPrimaryKeyUserMenu()
        {
            return dal.SelectOrderByPrimaryKeyUserMenu(conn);
        }

        public List<UserMenu> SelectGroupByPrimaryKeyUserMenu()
        {
            return dal.SelectGroupByPrimaryKeyUserMenu(conn);
        }

        public List<UserMenu> SelectMenusByApplicationID(UserMenu usermenu)
        {
            return dal.SelectMenusByApplicationID(conn, usermenu);
        }
        #endregion
    }
}

目前这个商业类的方法都比较简单，如果有比较复杂的，可能一个商业方法里需要调用数据访问的方法好多个，在做一些逻辑判断。那么这些商业方法就可以变得复杂多了。如这样的一个商业方法：

        public bool MoveUpItem(UserMenuItem usermenuitem)
        {
            usermenuitem = dal.FindAUserMenuItem(conn, usermenuitem);
            UserMenuItem previousMenuItem = dal.SelectPreviousMenuItem(conn, usermenuitem);
            int iTempOrdinal = usermenuitem.Ordinal;
            usermenuitem.Ordinal = previousMenuItem.Ordinal;
            previousMenuItem.Ordinal = iTempOrdinal;
            dal.UpdateUserMenuItem(conn, usermenuitem);
            dal.UpdateUserMenuItem(conn, previousMenuItem);
            return true;
        }

Unity配置信息：

  <unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
    <sectionExtension type="Microsoft.Practices.Unity.InterceptionExtension.Configuration.InterceptionConfigurationExtension, Microsoft.Practices.Unity.Interception.Configuration" />
    <namespace name="BusinessLogic" />
    <container name="myContainer">
      <extension type="Interception" />
      <register type="BusinessLogic.IBLLApplication, BusinessLogic" mapTo="BusinessLogic.BLLApplication, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLDomain, BusinessLogic" mapTo="BusinessLogic.BLLDomain, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLFormElement, BusinessLogic" mapTo="BusinessLogic.BLLFormElement, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLUserAccount, BusinessLogic" mapTo="BusinessLogic.BLLUserAccount, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLUserColumns, BusinessLogic" mapTo="BusinessLogic.BLLUserColumns, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLUserForm, BusinessLogic" mapTo="BusinessLogic.BLLUserForm, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLUserMenu, BusinessLogic" mapTo="BusinessLogic.BLLUserMenu, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLUserMenuItem, BusinessLogic" mapTo="BusinessLogic.BLLUserMenuItem, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLUserSession, BusinessLogic" mapTo="BusinessLogic.BLLUserSession, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <register type="BusinessLogic.IBLLUserTables, BusinessLogic" mapTo="BusinessLogic.BLLUserTables, BusinessLogic">
        <interceptor name="myinterceptor" type="InterfaceInterceptor" isDefaultForType="true" />
        <policyInjection />
      </register>
      <interception>
        <policy name="mypolicy">
          <callHandler name="myHandler1" type="BusinessLogic.MyDBHandler, BusinessLogic"></callHandler>
          <matchingRule name="myrule" type="CustomAttributeMatchingRule">
            <constructor>
              <param name="attributeType" type="System.Type, mscorlib">
                <value value="BusinessLogic.MyDBHandlerAttribute, BusinessLogic" typeConverter="BusinessLogic.GetTypeConverter, BusinessLogic" />
              </param>
              <param name="inherited" type="bool">
                <value value="true" />
              </param>
            </constructor>
          </matchingRule>
        </policy>
      </interception>
    </container>
  </unity>

注意到这些register的节点没有？这些节点实现了接口到具体商业类的映射。接口表示的是一个抽象。它只有方法的声明，没有具体实现。在调用者需要一个具体的实现了这个接口的商业类时，容器帮助我们创建这个商业类的实例，而接口到商业类的映射就是在Unity配置文件里做的。
Unity除了帮助我们实现接口到商业类的映射，还可以帮助我们实现aop. 比如log, db transaction, exception handling.

using System;
using System.Data;
using System.Data.Common;
using System.Collections.Generic;
using Microsoft.Practices.Unity.InterceptionExtension;
using DataAccessCommon;
using CommonUtil;

namespace BusinessLogic
{
    public class MyDBHandler : ICallHandler
    {
        private int iOrder = 0;

        public IMethodReturn Invoke(IMethodInvocation input, GetNextHandlerDelegate getNext)
        {
            var retvalue = getNext()(input, getNext); // call the intercepting method
            if (retvalue.Exception != null)
            {
                SysLog.GetInstance().LogError(retvalue.Exception);
            }
            return retvalue;
        }

        public int Order
        {
            get
            {
                return iOrder;
            }
            set
            {
                iOrder = value;
            }
        }
    }
}

这个MyDBHandler已经在之前的Unity配置中指定了。即这句：

<callHandler name="myHandler1" type="BusinessLogic.MyDBHandler, BusinessLogic"></callHandler>

这句是去调用被拦截的方法：

retvalue = getNext()(input, getNext);

被拦截方法（即我们的商业方法）返回以后，程序就检查retvalue.Exception有没有出错，有就调用logging的类来写log。将出错信息完整地打印出来。
自定义的attribute类：

using System;
using System.Collections.Generic;
using Microsoft.Practices.Unity;
using Microsoft.Practices.Unity.InterceptionExtension;
namespace BusinessLogic
{
    public class MyDBHandlerAttribute : HandlerAttribute
    {
        public override ICallHandler CreateHandler(IUnityContainer container)
        {
            return new MyDBHandler();
        }
    }
}

至于db transaction, 如果数据库事务比较简单，可以用TransactionScope，前面的MyDBHandler的invoke方法就替换成这样。

                using (TransactionScope ts = new TransactionScope())
                {
                    var retvalue = getNext().Invoke(input, getNext);
                    if (retvalue.Exception != null)
                    {
                        SysLog.GetInstance().LogError(retvalue.Exception);
                    }
                    else
                    {
                        ts.Complete();
                    }
                    return retvalue
                }

Unity配置里用到的一个工具类代码：

using System;
using System.Collections.Generic;
using Microsoft.Practices.Unity;
using Microsoft.Practices.Unity.InterceptionExtension;
namespace BusinessLogic
{
    public class GetTypeConverter : System.ComponentModel.TypeConverter
    {
        public override object ConvertFrom(System.ComponentModel.ITypeDescriptorContext context,
            System.Globalization.CultureInfo culture,
            object value)
        {
            return Type.GetType(value.ToString());
        }
    }
}

这个类用来做类型转换的。用来帮助Unity来找自定义的MyDBHandlerAttribute的。

商业类的调用者

为了调用商业类，我们有一个类来帮助创建相应的商业类的实例：

using System;
using System.Collections.Generic;
using Microsoft.Practices.Unity;
using Microsoft.Practices.Unity.Configuration;

namespace BusinessLogic
{
    public static class BusinessClassCreator
    {
        public static IUnityContainer container = new UnityContainer().LoadConfiguration("myContainer");

        public static T GetInstance<T>()
        {
            return (T)container.Resolve(typeof(T), null);
        }

        public static object GetInstance(Type type)
        {
            return container.Resolve(type, null);
        }
    }
}

在调用的地方代码这么写：

        [HttpGet]
        public ActionResult SaveMenuScheme()
        {
            UserMenu userMenu = new UserMenu();
            userMenu.MenuID = GetMenuID(this);
            userMenu = BusinessClassCreator.GetInstance<IBLLUserMenu>().FindAUserMenu(userMenu);
            short bMenuScheme = 0;
            bMenuScheme = (short)DesignTableController.GetID(this);
            userMenu.Scheme = bMenuScheme;
            BusinessClassCreator.GetInstance<IBLLUserMenu>().UpdateUserMenu(userMenu);
            return DisplayMenuList();
        }

这是一个在asp.net mvc中调用上述商业类的样例代码，首先通过BusinessClassCreator.GetInstance<IBLLUserMenu>()得到接口IBLLUserMenu对应的商业类对象，然后再调用IBLLUserMenu接口上的方法。比如此例中调用了FindUserMenu方法和UpdateUserMenu方法。每个方法的返回类型已经由接口定义好。我们只要按照这个接口的定义来使用这个接口就可以了。接口在这里的好处就是它定义了商业类的规范，所有实现此接口的商业类都符合此接口的规范。而且具体实现和接口定义是分离的。这样我们就可以单独改变实现接口的商业类。商业类的调用者既可以是一个asp.net mvc的程序，也可以是一个asp.net web form的，还可以是一个winform程序。

 demo代码下载： http://dl.vmall.com/c08haaatpu， 博客园这里上传不了。没有办法。只能选别处了。