Linq笔记

—————Linq多表连接查询————

 

var List= from v in      db.BaseMachines
                       join   b    in   db.Doors    on    v.MachineID   equals   b.BaseMachineID
                       where   v.MachineCode.StartsWith(AreaCode)   &&    v.MachineType == 505     
                       select b;

 

SQL语句表达： select  * from   BaseMachines  a,  Doors   b where  a.MachineID =b.BaseMachineID  AND a.MachineCode like 'AreaCode%'   &&    a.MachineType == 505     

————Linq分组查询————

var list = from v in db.Role_Machine
                       where v.RoleID==RoleID
                       group v by v.MachineType into g
                       select new
                       {
                           g.Key,
                           Count = g.Count()
                       }; 

SQL语句表达：  select COUNT(DeviceID) DeviceID,MachineType   from   Role_Machine   group  by   MachineType