Linq 应用

1.Linq  Group

string[] arr={"www.baidu.com","www.aa.cn","www.bb.com","www.cbc.net","www.abc.com.cn","aaa"};

var arrs=from item in arr where item.LastIndexOf(".")!=-1 group by  item.SubString(item.LastIndexOf(".")) 

2  Linq into

var arrs= from item in arr where item.LastIndexOf(".")!=-1 group by  item.SubString(item.LastIndexOf("."))
into ite where ite.Count()==3

3. Linq let

 var arrs= from item in arr let ite= item.LastIndexOf(".")!=-1 group by item.SubString(ite);