13 MVC------------EF的带Lambada表达式的分页通用方法

/// <summary>
/// 终极版带lambada表达式的分页查询
/// </summary>
/// <typeparam name="T">获取的分页实体的类型</typeparam>
/// <param name="whereLambada">查询符合条件的lambada表达式</param>
/// <param name="orderByLambada">分页根据什么字段进行排序</param>
/// <param name="pageSize">一页多少条数据</param>
/// <param name="pageIndex">当前页数</param>
/// <param name="isDes">是否降序排列</param>
/// <param name="total">总记录条数</param>
/// <returns>获取当前页数的实体对象</returns>
static List<dynamic> GetPageList<T>(Expression<Func<T,dynamic> >selector, Expression<Func<T,bool>> whereLambada,Expression<Func<T,object>> orderByLambada,int pageSize,int pageIndex,out int total,bool isDes) where T:class

{
//获取数据库模板的上下文对象
TestOAEntities context = new TestOAEntities();
//获取总记录数
total = context.Set<T>().Count();
//skip()==跳跃，越过多少列 Take==获取多少条
var result = context.Set<T>().Where(whereLambada);
if (isDes)
{
result.OrderByDescending(orderByLambada);
}
else
{
result.OrderBy(orderByLambada);
}
var pgList = result.Skip((pageIndex-1)*pageSize).Take(pageSize).Select(selector);
return pgList.ToList();
}

//演化的由来
        //第一步先查询出所有的符合要求的实体对象
        static List<T> GetPageList<T>(Expression<Func<T,bool>> whereLambada) where T:class
        {
            //获取数据库模板的上下文对象
            TestOAEntities context = new TestOAEntities();
            //在where查询中要求传入的是一个当前实体的类型，传出的是一个bool类型的条件
            //select(s=>s)表示选择所有的列，当只需要部分列的时候，select(s=>new{s.SID,s.SName})
            var pgList = context.Set<T>().Select(s => s).Where(whereLambada);
            return pgList.ToList();
        }

        //第二步根据要排序的字段进行排序
        static List<T> GetPageList<T>(Expression< Func<T, bool>> whereLambada, Expression<Func<T, object>> orderByLambada)
            where T:class
        {
            TestOAEntities context = new TestOAEntities();
            var pgList= context.Set<T>().Select(s=>s).Where(whereLambada).OrderByDescending(orderByLambada);
            return pgList.ToList();//取消延迟加载
        }
        //传入当前分页，和一页几条数据的值
        static List<T> GetPageList<T>(Expression<Func<T,bool>> whereLambada,Expression<Func<T,object>> orderByLambada,int pageSize,int pageIndex) where T:class
        {
            TestOAEntities context = new TestOAEntities();
            var pgList= context.Set<T>().Select(s => s).Where(whereLambada).OrderByDescending(orderByLambada).Skip((pageIndex - 1) * pageSize).Take(pageSize);
            return pgList.ToList();
        }

13 MVC------------EF的带Lambada表达式的分页通用方法

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