简单三层备忘

1.实例层

using System;
using System.Collections.Generic;
using System.Text;

namespace OA.Entity
{
    public class user
    {
        private int _id;

        public int Id
        {
            get { return _id; }
            set { _id = value; }
        }
        private string _name;

        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }
    }
}

---

2.数据访问接口（引用实体）

using System;
using System.Collections.Generic;
using System.Text;

namespace OA.IDAL
{
   
        public interface user
        {
            OA.Entity.user LoadById(int id);
        }

   
}

---

3.数据访问实现（引用实体和接口）参照此实现可以根据接口写其它数据库实现

using System;
using System.Collections.Generic;
using System.Text;

namespace OA.SQLProvider
    
{
    public class user:OA.IDAL.user
    {
        public OA.Entity.user LoadById(int id)
        {
            if (id==1)
            {
                OA.Entity.user list = new Entity.user
                {
                    Id = 1,
                    Name = "TEST NAME"
                };
               return list;
            }
            else
            {

                OA.Entity.user list = new Entity.user
                {
                    Id = 0,
                    Name = "null"
                };
                return list;
            }
             
        }
    }
}

---

4.BLL业务逻缉层（引用实体。接口。工厂）

using System;
using System.Collections.Generic;
using System.Text;

namespace OA.BLL
{
    public class user
    {
        public OA.Entity.user  ById(int id)
         {
            OA.IDAL .user ProviderClass= DALFactory .DataAccess.CreateObject <OA.IDAL .user >();

        return ProviderClass .LoadById(id);
        }
    }
}

5.数据工厂

using System;
using System.Collections.Generic;
using System.Text;
using System.Web;

namespace OA.DALFactory
{
    /// <summary>
    /// 抽象工厂模式创建DAL-(利用工厂模式+泛型机制+反射机制+缓存机制,实现动态创建不同的数据层对象接口) 。
    /// 可以在这个DataAccess类里创建所有DAL类
    /// </summary>
    public sealed class DataAccess
    {
        /// <summary>
        /// 数据访问的具体实现
        /// </summary>
        private static readonly string path = System.Web.HttpContext.Current.Server.MapPath("~/DataProviders/" + System.Web.Configuration.WebConfigurationManager.AppSettings["dllname"]);

        /// <summary>
        /// 采用泛型创建对象或从缓存获取
        /// </summary>
        /// <typeparam name="T">数据类型</typeparam>
        /// <returns>确定类型的对象</returns>
        public static T CreateObject<T>()
        {
            // 此处可采用XML或者配置文件，把对应关系做的更加灵活             
            //string typeName = "OA.DALSQLProvider." + typeof(T).Name;//OA.DALSQLProvider .User 
            string provider = System.Web.Configuration.WebConfigurationManager.AppSettings["Provider"];
            string typeName = provider + "." + typeof(T).Name;
           
            object obj;

            // 从缓存中读取数据
            obj = System.Web.HttpContext.Current.Cache.Get(typeName);

            // 创建新的实例
            if (obj == null)
            {   // 反射创建
                obj = System.Reflection.Assembly.LoadFile(path).CreateInstance(typeName);
                System.Web.HttpContext.Current.Cache.Add(typeName, obj, null, System.Web.Caching.Cache.NoAbsoluteExpiration, System.Web.Caching.Cache.NoSlidingExpiration, System.Web.Caching.CacheItemPriority.Normal, null);    // 放入缓存中
            }
            return (T)obj;
            
        }
    }
}

6.UI（引用实体，业务）

 protected void Button1_Click(object sender, EventArgs e)
        {
            OA.BLL.user user = new OA.BLL.user();
            OA.Entity.user list = new Entity.user();
            list = user.ById(1);
            this.Label1.Text = list.Name;
        }

WEB方式的WEBCONFIG（改变此处即可以实现调用不同数据库）

 <appSettings>

    <add  key ="dllname" value ="OA.SQLProvider.dll"/>
    <add key="Provider" value="OA.SQLProvider"/>
  </appSettings>

 复制OA.SQLProvider.dll到"~/DataProviders/“下面，此处与WEBCONFIG配合实现调用不同的数据库）