Group Datatable by Value and Joining Row values

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have a look here:

give a try

Assign Activity:
dtResult = MainDT.Clone

Assign Activity:
dtResult =

(From d In MainDT.AsEnumerable
Group d By k=d("WorkOrderNo").toString.Trim Into grp=Group
Let ts = grp.Select(Function (t) t("Task").toString.Trim)
Let tj = String.Join(" ", ts.Select(Function (tn, i) (i+1).toString &". " & tn))
Let rf = grp.First()
Let ra = New Object(){rf(0), rf(1), k, rf(3), rf(4), tj}
Select r = dtResult.Rows.Add(ra)).CopyToDataTable
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