/// <summary>/// 1.数据会话层：就是一个工厂类，负责完成所有数据操作类实例的创建，然后业务层通过数据会话层来获取要操作数据类的实例，/// 所以数据会话层将业务层和数据层解耦。/// 2.在数据会话层中提供一个方法：完成所有数据的保存。/// </summary>public class DBSession{OAEntities Db = new OAEntities();private IUserInfoDal _UserInfoDal;public IUserInfoDal UserInfoDal{get{if(_UserInfoDal==null){_UserInfoDal=new UserInfoDal();}return _UserInfoDal;}set{_UserInfoDal = value;}}/// <summary>/// 一个业务中经常涉及到对多张表的操作，我们希望连接一次数据库，完成对这张表数据的操作，提高性能        /// 工作单元模式/// </summary>/// <returns></returns>public bool SaveChanges(){return Db.SaveChanges() > 0;}}

  public class BaseDal<T> where T : class, new(){OAEntities Db = new OAEntities();/// <summary>/// 新增/// </summary>/// <param name="entity"></param>/// <returns></returns>public T AddEntity(T entity){Db.Set<T>().Add(entity);//DbSet<T>//Db.SaveChanges();return entity;}/// <summary>/// 删除/// </summary>/// <param name="entity"></param>/// <returns></returns>public bool DeleteEntity(T entity){//追加到ef上，打上删除标记，再保存Db.Entry<T>(entity).State = System.Data.Entity.EntityState.Deleted;//return Db.SaveChanges() > 0;return true;}/// <summary>/// 更新/// </summary>/// <param name="entity"></param>/// <returns></returns>public bool EditEntity(T entity){//追加到ef上，打上编辑标记，再保存Db.Entry<T>(entity).State = System.Data.Entity.EntityState.Modified;//return Db.SaveChanges() > 0;return true;}/// <summary>/// 查询过滤/// </summary>/// <param name="whereLambda"></param>/// <returns></returns>public IQueryable<T> LoadEntities(Expression<Func<T, bool>> whereLambda){return Db.Set<T>().Where(whereLambda);}/// <summary>/// 分页/// </summary>/// <typeparam name="s"></typeparam>/// <param name="pageIndex">页码</param>/// <param name="pageSize">每页数量</param>/// <param name="totalCount">总数</param>/// <param name="whereLambda">过滤条件</param>/// <param name="orderbyLambda">排序条件</param>/// <param name="isAsc"></param>/// <returns></returns>public IQueryable<T> PageLoadEntities<s>(int pageIndex, int pageSize, out int totalCount, Expression<Func<T, bool>> whereLambda, Expression<Func<T, s>> orderbyLambda, bool isAsc){var temp = Db.Set<T>().Where(whereLambda);totalCount = temp.Count();if (isAsc)//正序
            {//列：pageIndex=3,pageSize=15//正序排列后，跳过第3页前的数据(前2页*15)，剩下的只读取15条temp = temp.OrderBy<T, s>(orderbyLambda).Skip<T>((pageIndex - 1) * pageSize).Take<T>(pageSize);}else//倒序
            {temp = temp.OrderByDescending<T, s>(orderbyLambda).Skip<T>((pageIndex - 1) * pageSize).Take<T>(pageSize);}return temp;}}