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BOF

property BOF: Boolean read;

Example​

procedure MoveBeforeCurrent(const Data: TvxClientDataSet);
begin
  if not Data.BOF then
    Data.Prior;
end;

Usage​

BOF indicates that backward navigation is at the beginning boundary of the current dataset view.

  • Use Active plus IsEmpty, not BOF alone, to test for rows.
  • Check it in reverse loops and ensure Prior is called on every iteration path.
  • Cursor-changing callbacks can invalidate a previously read value.

Additional Technical Info​

BOF is declared by hidden ancestor TDataSet and is normally used through a visible descendant such as TvxClientDataSet. It is a cursor flag, not a record-number or empty-dataset property by itself.

Source-backed behaviour​

The base maintains FBOF through buffer activation/clear and relative navigation. First explicitly sets BOF true after positioning; a failed backward move also sets it true. Clearing/inactivating buffers sets both BOF and EOF true.

The flag describes the current filtered/indexed view and can change after filters, locate, post/delete or resynchronization. A nonempty dataset can legitimately have BOF true while positioned at its first row.

EOF is the forward boundary. First, Prior and MoveBy update it.

Official RTL references​

Created 2026-07-15