从两个集合里排除重复的写法（适用：DB表和字段都很多，表间有关联的情况）

获取其中一张表bulletinred为1的内容：

public IList<BRShow> GetBulInfo()
        {
            var result = from a in ((Entities)this.DataContext).SPEPBULLETIN
                         join b in ((Entities)this.DataContext).USERS on a.USERID.ToUpper() equals b.ACCOUNT.ToUpper()

                         orderby a.POSTDATE descending
                         select new BRShow { ID = a.ID, TITLE = a.TITLE, NAME = b.NAME, POST_LEVEL = a.POST_LEVEL, POSTCONTENT = a.POSTCONTENT, POSTDATE = a.POSTDATE, bulletinread = 0 }; //查询出所有信息

            //20140402  By Xudaxia  遍历result，取得为1的条数
            var result2 = (from r in result
                           join b in ((Entities)this.DataContext).BULLETIN_RECORDS
                           on r.ID equals b.ID
                           select r).ToList();
            foreach (var r in result2) { r.bulletinread = 1; };
            return result2;
        }

获取表所有信息：

public IList<BRShow> GetBulInfo1()
        {
            var spepbulletins = ((Entities)this.DataContext).SPEPBULLETIN.ToList();
            var users = ((Entities)this.DataContext).USERS.ToList();
            var result = from a in spepbulletins
                         join b in users on a.USERID.ToUpper() equals b.ACCOUNT.ToUpper()
                         orderby a.POSTDATE descending
                         select new BRShow { ID = a.ID, TITLE = a.TITLE, NAME = b.NAME, POST_LEVEL = a.POST_LEVEL, POSTCONTENT = a.POSTCONTENT, POSTDATE = a.POSTDATE}; //查处所有信息（含未读和已读）
            return result.ToList();
        }

在页面上调用，转为LIST后在所有信息中遍历取得ID，判断A表和B表的ID是否一致，如果一直则将bulletinred赋值为1

List<BRShow> list = bulRep.GetBulInfo().ToList();//查处所有已读信息
        List<BRShow> list1 = bulRep.GetBulInfo1().ToList();
        foreach (BRShow b in list)
        {
            if (list1.Where(l => l.ID == b.ID).First() != null)
                list1.Where(l => l.ID == b.ID).First().bulletinread = 1;
        }

最后取得所有相关内容

List<BRShow> tt = list1;

----附：欢迎大家提出更简便、性能更好的方法~