Set Transaction error

 

I am getting an error "SET TRANSACTION must be first statement of transaction." when I try to save an entity to the database. Below is the code. Please let me know in what circumstances this error would generate.

I appreciate your help. Thank you.

 

public static void SetMonth(OssMarginEntityManager em, DateTime beginDate, DateTime endDate)
        {
            var item = (from o in em.OssMarginMonths where (o.OssMarginMonthId == 1) select o).FirstOrNullEntity();

            if (item != null && item.OssMarginMonthId  >  0)
            {
                item.BeginDate = beginDate;
                item.EndDate = endDate;
                var entities = new List<Entity> { item };
                em.SaveChangesAsync(entities, SetMonthCallback, null);
            }
        }