IndexOf Returns negative one

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#1

I have the following:

  1. TransactionData as Datarow
  2. TransactionItem as Datarow, from TransactionData

I want to get the index of the TransactionItem using TransactionData.CopyToDatatable.Rows.IndexOf(TransactionItem) but it always returns negative one (-1). I change the TransactionData as Datatable and it returns correct results.