Linq连接查询

//inner join

var query = from a in data.A   

                   join b in data.B          

                  on a.bid equals b.id

                select new

　　　　    {

                        id=a.id,

                        name = b.name

　　　　    };

                 

 

//left join

var query = from a in data.A    

                   join b in data.B           

                  on a.bid equals b.id into ab       

                  from b in ab.DefaultIfEmpty()       

    　　　　  join c in data.C          

  　　　　　 on b.cid equals c.id into bc     

     　　　   from c in bc.DefaultIfEmpty()      

     　　　   join d in data.D           

 　　　　    on c.did equals d.id into cd         

   　　　　  from d in cd.DefaultIfEmpty()          

  　　　　   join e in data.E         

    　　　　 on d.eid equals e.id into ce       

     　　　  from e in ce.DefaultIfEmpty()          

  　　　　  select new

 　　   　　 {               

   　　　　　　    Id = a.Id,        

       　　　　     Name = b==null?"":b.Name,       

         　　　　   Pro = c==null?"":c.Pro,         

        　　　　   IpAdd = d==null?"":d.IpAdd       

    　　    };