using (var db = new BaikeEntities())
            {
                var param = Expression.Parameter(typeof(Article));
                var expr = Expression.GreaterThan(Expression.Property(param, "CreateDate"), Expression.Constant(minDate));
                expr = Expression.And(expr, Expression.GreaterThan(Expression.Property(param, "RowStatus"), Expression.Constant(0)));
                expr = Expression.And(expr, Expression.Equal(Expression.Property(param, "Limit"), Expression.Constant(0)));

                var lambda = Expression.Lambda>(expr, new ParameterExpression[] { param });
                var q = db.Articles
                   .Where(lambda)
                   .OrderByDescending(p => p.CreateDate)
                   .Take(count);
               
                /ar q = db.Articles
                //   .Where(a => a.RowStatus == 0 & a.Limit == 0& a.CreateDate >= minDate)
                //   .OrderByDescending(p => p.CreateDate)
                //   .Take(count);
                //articles = q.ToList();
            }
优化前：

 SELECT
`Extent1`.`ArticleId`, 
`Extent1`.`KmArticleId`, 
`Extent1`.`KmCategoryId`, 
`Extent1`.`KmCategory`, 
`Extent1`.`KmParentCategoryId`, 
`Extent1`.`KmParentCategory`, 
`Extent1`.`KmGroupId`, 
`Extent1`.`KmGroup`, 
`Extent1`.`Title`, 
`Extent1`.`Intro`, 
`Extent1`.`Content`, 
`Extent1`.`Url`, 
`Extent1`.`ReadCount`, 
`Extent1`.`ReplyCount`, 
`Extent1`.`BookmarkCount`, 
`Extent1`.`DiggCount`, 
`Extent1`.`Authorship`, 
`Extent1`.`Staff`, 
`Extent1`.`DepartmentId`, 
`Extent1`.`CreateDate`, 
`Extent1`.`Selected`, 
`Extent1`.`IsCreateFromBaike`, 
`Extent1`.`BaikeProjectId`, 
`Extent1`.`RowStatus`, 
`Extent1`.`IsKMAllow`, 
`Extent1`.`Limit`, 
`Extent1`.`Attachments`, 
`Extent1`.`ComeFrom`, 
`Extent1`.`Type`, 
`Extent1`.`Hot`, 
`Extent1`.`Rank`, 
`Extent1`.`LastOperateTime`, 
`Extent1`.`OriginalUrl`, 
`Extent1`.`VideoAttas`
FROM `Article` AS `Extent1`
 WHERE ((`Extent1`.`CreateDate` > @gp1) AND (0 = `Extent1`.`RowStatus`)) AND (0 = `Extent1`.`Limit`)
 ORDER BY 
`Extent1`.`CreateDate` DESC LIMIT 5