linq to sql取出随机记录/多表查询/将查询出的结果生成xml

在手写sql的年代，如果想从sqlserver数据库随机取几条数据，可以利用order by NewId()轻松实现，要实现多表查询也可以用select * from A,B Where A.ID=B.ID做到，但这些功能到了linq to sql中如何实现呢？

关键点:
1.随机排序问题:可以用 Select(d=> new {NewId=new Guid()}).OrderBy(d=>d.NewId)达到order by NewId()的效果
2.多表查询
from a in TableA
from b in TableB
where a.ID == b.ID

另外利用linq to xml还可以轻易将查询出来的结果保存成xml(这一点比传统xml的方法确实要新颖很多)

详细代码可参考我在一个项目中的示例(功能为随机取机10条产品视频的记录，并生成xml供播放器调用)

using (DBDataContext db = new DBDataContext(Database.ConnectionString))
        ...{
            var q = db.T_Shops.Where(s => s.F_ID == new Guid("00000000-0000-0000-0000-000000000001")).Select(s => new ...{ s.F_AutoID }).First();
            string _ShopAutoId = q.F_AutoID.ToString();

            var query = (from v in db.V_ProductVideos
                         from pv in db.V_ProductTV
                         where v.F_ShopID == new Guid("00000000-0000-0000-0000-000000000001") &&
                               v.F_ProductID == pv.F_ID &&
                               pv.F_Status == 1 &&
                               pv.F_isShow == 1 &&
                               v.F_Status == 1 &&
                               v.F_isShow == 1 &&
                               v.F_ProductStatus == 1
                         select new
                         ...{
                             v.F_VideoS,
                             v.F_VideoP,
                             v.F_VideoW,
                             v.F_VideoL,
                             v.F_ClsAutoID,
                             v.F_ProductName,
                             v.F_ProductAutoID,
                             NewId = Utils.NewComb()
                         }
                         ).OrderBy(p => p.NewId).Take(10);

            //利用linq to xml生成xml
            XDocument doc = new XDocument(
                new XElement("flvLists", from d in query
                                         select (
                                                            new XElement(
                                                                "item",
                                                                new XAttribute("title_p", d.F_VideoP),
                                                                new XAttribute("title_s", d.F_VideoS),
                                                                new XAttribute("name", Utils.NoHtml(d.F_ProductName, 500)),
                                                                new XAttribute("link", "http://www.cntvs.com/product/" + d.F_ClsAutoID.ToString() + "/" + _ShopAutoId + "/" + d.F_ProductAutoID)
                                                            ))));


            doc.Save(Server.MapPath("~/upload/xml/tvvideo.xml"));

            db.Connection.Close();

           
        }