linq c中的if子句

Question

我有以下LINQ语句，我需要写内部，if子句，我做了以下但显然是一个错误，我问我怎样才能在LINQ中实现这样的东西？

var devices = (from c in db.MasterDatas
               join m in db.TurbineDevices on
               c.turbine_id equals m.turbine_ip
               join t in db.v_vpn_gateway_info
               on m.turbine_ip equals t.turbine_id
               where m.turbine_ip == id                  

               select new TurbineDvce
               {
                  if(t.vpn_gateway==m.device_ip)
                      {Comments =vpn_gateway

                           }else

                   Comments = m.comments,
                   Description = m.description,
                   DeviceIP = m.device_ip,
                   DeviceType = m.device_type,
                   FirmwareVersion = m.firmware_version,
                   Model = m.model,
                   Password = m.psw,
                   Phone = m.tel_number,
                   Producer = m.producer,
                   PublicIP = m.public_ip,
                   TurbineId = m.turbine_ip,
                   Username = m.username
               });