internal static TableRowBookmark?New(TableRowSet trs)
{
return((trs._tb.rows.First() is Bookmark <ValueTuple <long, long> > b) ?
new TableRowBookmark(trs, b, 0) : null);
}
protected TableRowBookmark(TableRowSet trs, Bookmark <ValueTuple <long, long> > bm, int p)
: base(trs, new SRow(trs._tr, trs._tr.Get(bm.Value.Item2)), p)
{
_trs = trs; _bmk = bm;
}