select * from dbo."Batches" inner join dbo.StudentBatchRelation
  on dbo.Batches.Id = dbo.StudentBatchRelation.BatchId where
  dbo.StudentBatchRelation.StudentId = '3d980306-e36e-4581-8c98-219717cb1668'

var result = (from t1 in contBatch.GetallBatchList()
                         join t2 in contStudent.getAllStudentBatchList()
                         on t1.Id equals t2.batchId where t2.studentId == studentid
                        select new { t1.Days, t1.BatchDate }).ToList();