//请各位大虾帮帮忙弄了我好多天了

               DataContext con = new DataContext();
                 Survey entity = null;//接收的实体对象
                 DataLoadOptions dl = new DataLoadOptions();
                    dl.LoadWith<Survey>(c => c.SurveyAnswers);//关联SurveyAnswers表
                                con.LoadOptions = dl;
                entity = (from su in con.Surveys

                           //where中我想让SurveyAnswers表的id等于传过来的id
                          where  su.ID == ID //&& SurveyAnswers.ID == AnswerID
                          select su).SingleOrDefault();