Optimize speed in removing duplicate records from a datatable.

I am trying to remove duplicate rows from a datatable. The datatable was created by parsing out a MemoryStream and there is no way to change that part of the code. I can do the following code and remove any duplicate records. However it is slow and the more rows there are the worse it gets. There must be a better way but I'm not sure how. Is there a way to query the datatable directly in Visual Basic to return rows that match so i dont have to loop through every single record?

Private Sub FilterFaster(ByRef tbl As DataTable)
Dim copyTable As DataTable = tbl.Copy
    For Each r As DataRow In copyTable.Rows
        Dim foundOne As Boolean = False
        For i As Integer = (tbl.Rows.Count - 1) To 0 Step -1
            If CompareRows(r, tbl.Rows(i)) Then
                If foundOne Then
                    ' delete the row from the primary table
                    tbl.Rows(i).Delete()
                Else
                    ' this is the first instance of duplication, it is ok
                    foundOne = True
                End If
            End If
        Next
    Next
copyTable.Dispose()
end sub

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