give a try on following
Clone your datatable (ensure the Result column holding failed, success is not present) - dtResult
Add a datacolumn (should be on end of columns) ColName Result
Assign activity
Left: dtResult
right
(From d in dtData.AsEnumerable
let chl = d(Col1).toString.Trim.Equals(d(Col2).toString.Trim)
Let res = If(chk, “Success”, “Failed”)
Let ra = d.ItemArray.Append(res).toArray
Select r=dtResult.Rows.add(ra)).CopyToDataTable