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A DataTable in ADO.NET has no concept of a 'current row' because, once it's been populated, it's disconnected from the underlying database. In fact, it doesn't need to have an underlying database at all - it can be created entirely using code!
Once you have your DataTable (dt, say), you can iterate through its DataRows just like any other collection:
foreach(DataRow dr in dt.Rows)
{
// do something with dr
}
You can also obtain a DataRow directly:
DataRow rowFirst = dt.Rows[0];
DataRow rowLast = dt.Rows[dt.Rows.Count - 1];
It follows that there's no concept of being before the first row or after the last row (BOF or EOF in an ADO RecordSet). You must always be within the row collection itself or you'll get an exception.