泛型+反射+三层实现工厂

1、Web.config配置文件

<appSettings>
    <add key="webpages:Version" value="3.0.0.0"/>
    <add key="webpages:Enabled" value="false"/>
    <add key="ClientValidationEnabled" value="true"/>
    <add key="UnobtrusiveJavaScriptEnabled" value="true"/>
    <add key="DAL" value="DAL"/>
  </appSettings>

2、Model层创建BaseModel定义一个空的抽象类

//BaseModel  定义一个空的接口
    public abstract class BaseModel
    {
    }

3、DAL层定义接口并实现方法；  Factory代码如下：

//Factory
    public class Factory<T> where T:class
    {
        //获取配置文件
        private static readonly string path = Path.Combine(
            ConfigurationManager.AppSettings["DAL"]
            );
        private Factory() { }
        //创建实例 反射创建实例
        public static T CreateDAL(string type)
        {
            string className= string.Format(path+".{0}",type);
            try
            {
                return (T)System.Reflection.Assembly.Load(path).CreateInstance(className);
            }
            catch (Exception)
            {

                throw;
            }
        }
    }

4、BLL层定义BaseBll类：

public class BaseBll<T> where T : Model.BaseModel, new()
    {
        protected IDataServer<T> Dal;
        public BaseBll(string type)
        {
            //通过工厂得到实例
            Dal = Factory<IDataServer<T>>.CreateDAL(type);
        }
        public virtual int Add(T t)
        {
            return Dal.Add(t);
        }
        public virtual int Del(int id)
        {
            return Dal.Del(id);
        }
        public virtual int Upt(T t)
        {
            return Dal.Upt(t);
        }
        public virtual List<T> GetAll()
        {
            return Dal.GetAll();
        }
        public virtual List<T> GetAllById(int id)
        {
            return Dal.GetAllById(id);
        }
    }

5、Bll层继承BaseBll，采用单例模式实现方法：

public class StudentBll:BaseBll<StudentInfo>
    {
        private const string _Type = "StudentDal";
        private IDataServer<StudentInfo> _DAL;
        public StudentBll() : base(_Type)
        {
            _DAL = base.Dal as IDataServer<StudentInfo>;
            if (_DAL == null)
            {
                throw new NullReferenceException(_Type);
            }
        }
        public List<StudentInfo> GetList()
        {
            return _DAL.GetAll();
        }
    }