Linq group by and concatenate

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This is the syntax used:

(From d In outDt.AsEnumerable
Group d By k=d(“A”).toString.Trim, k1=d(“B”).toString.Trim, k2=d(“C”).toString.Trim Into grp=Group
Let n = String.Join(“,”,grp.Select(Function (x) x(“old”).toString.Trim).toArray)
Let f = String.Join(“,”,grp.Select(Function (x) x(“New”).toString.Trim).toArray)
Let ra = New Object(){k,k1,k2,n,f}
Select dtReport.Rows.Add(ra)).CopyToDataTable

It works, the problem is: if i’ve some other columns to display in the new DT, how do I insert them into the new object?