Comma separated string using Linq

var dtReference = new DataTable("Reference");
var dtRefContext = new DataTable("RefContext");
var dtOutput = new DataTable("Output");

dtReference.Columns.AddRange
    (
        new DataColumn[]
        {
            new DataColumn("ReferenceId", typeof (int)),
            new DataColumn("Name", typeof (string)),
            new DataColumn("Desc", typeof (string))
        }
    );

dtRefContext.Columns.AddRange
    (
        new DataColumn[]
        {
            new DataColumn("ContextId", typeof (int)),
            new DataColumn("ReferenceId", typeof (int)),
            new DataColumn("ChildList", typeof (string))
        }
    );

dtOutput.Columns.AddRange
    (
        new DataColumn[]
        {
            new DataColumn("ReferenceName", typeof (string)),
            new DataColumn("ReferenceList", typeof (string))

        }
    );


for (int i = 1; i <= 6; i++)
{
    var rowRef = dtReference.NewRow();
    rowRef["ReferenceId"] = i;
    rowRef["Name"] = "Ref" + i;
    rowRef["Desc"] = "test" + i;
    dtReference.Rows.Add(rowRef);
}


var rowCon = dtRefContext.NewRow();
rowCon["ContextId"] = 1;
rowCon["ReferenceId"] = 1;
rowCon["ChildList"] = "2,3";
dtRefContext.Rows.Add(rowCon);

rowCon = dtRefContext.NewRow();
rowCon["ContextId"] = 2;
rowCon["ReferenceId"] = 4;
rowCon["ChildList"] = "1,5,6";
dtRefContext.Rows.Add(rowCon);



var _aa =
    from a in dtReference.AsEnumerable()
    from b in dtRefContext.AsEnumerable()
    where b.Field<int>("ReferenceId") == a.Field<int>("ReferenceId")
    select new
    {
        tempName = a.Field<string>("Name"),
        tempNameList = b.Field<string>("ChildList").Split(',').Select(int.Parse)
    };

var _bb =
    from a in dtReference.AsEnumerable()
    from b in _aa
    where b.tempNameList.Contains(a.Field<int>("ReferenceId"))
    select new
    {
        tempName = b.tempName,
        tempNameList = a.Field<string>("Name"),
    };

var result =
    from r in _bb
    group r by r.tempName into g
    select new
    {
        ReferenceName = g.Key,
        ReferenceList = string.Join(",", g.OrderBy(s => s.tempName)
                                   .Select(s => s.tempNameList))
    };

foreach (var item in result)
{
    var rowOut = dtOutput.NewRow();
    rowOut["ReferenceName"] = item.ReferenceName;
    rowOut["ReferenceList"] = item.ReferenceList;
    dtOutput.Rows.Add(rowOut);
}