LinQ表达式

1.从老集合中查询每一个元素存入新集合

var newlist=from u in ulist select u;

2.where条件

var newlist=from d in dlist where d.id="001"&&d.num=10 select d;

3.order by

var newlist=from d in dlist where d.id="001
                  order by d.id order by d.num select d;

4.join

var newlist=from d in dlist 
                  join d in dlist
                  on u.id equal d.id
                  select   new{
                        name=u.name;
                        num =d.num
                    }                

5.group by

var newlist=from d in dlist group u by u.id;

foreach(var g in newlist){
    foreach(var item in g){

    }
}