Group by and Sub group in Linq

Created a result set (Using IBATIS.NET Datamapper technology to load object using Stored Procedure method) as on object.

IList<CLASS1> objReport1 = new List<CLASS1>();

IList<CLASS> objReportBase = DataLayer.MethodName(strParam, 1, "N");

if (objReportBase.Count > 0)

{

               objReportNew = (from p in objReportBase

                                group p by new

                                {

                                    p.USERID,

                                    p.DISPLAYUSERID,

                                    p.LASTNAME,

                                    p.FIRSTNAME

                                } into g

                                orderby g.Key.LASTNAME, g.Key.SUITENAME

                                select new CLASS1

                                {

                                    USERID = g.Key.USERID,

                                    DISPLAYUSERID = g.Key.DISPLAYUSERID,

                                    LASTNAME = g.Key.LASTNAME,

                                    FIRSTNAME = g.Key.FIRSTNAME,

                                   

                                    subPVCs = g.Select(l => new

                                                {

                                                    l.COURSENAME,

                                                    l.MASTEREDDATE,

                                                    l.ASSIGNEDDATE,

                                                    l.MASTEREDSCORE,

                                                }

                                             ).Distinct()

                                }).ToList<CLASS1>();

                objReportBase = null;

}

           

public class BASECLASS

{

        public virtual int USERID { get; set; }

        public virtual string DISPLAYUSERID { get; set; }

        public virtual string LASTNAME { get; set; }

        public virtual string FIRSTNAME { get; set; }

        public virtual string COURSENAME { gets; set; }

        public virtual string MASTEREDDATE { get; set; }

        public virtual string ASSIGNEDDATE { get; set; }

        public virtual string MASTEREDSCORE { get; set; }

}

public class CLASS1

{

        public virtual int USERID { get; set; }

        public virtual string DISPLAYUSERID { get; set; }

        public virtual string LASTNAME { get; set; }

        public virtual string FIRSTNAME { get; set; }

        public virtual IEnumerable subPVCs { get; set; }

}

public class subPVC

{

        public virtual int USERID { get; set; }

        public virtual string COURSENAME { gets; set; }

        public virtual string MASTEREDDATE { get; set; }

        public virtual string ASSIGNEDDATE { get; set; }

        public virtual string MASTEREDSCORE { get; set; }

}