Author: Tomas Rutkauskas

I want to check if the user has filled all required DBEdit controls on a notebook, 
before enabling a button on the form.

Answer:

If you dropped the controls onto the notebook at design time, their Owner will be 
the form not the notebook. This means that it will not belong to the Components 
array of the notebook, but of the form. The Notebook's Controls array will be all 
the controls it parents and that is probably the array you want to loop through.

1   procedure TAddFrm.SetNextBtn;
2   var
3     I: Integer;
4     fld: TControl;
5     fldEmpty: Boolean;
6   begin
7     fldEmpty := False;
8     with Notebook do
9     begin
10      for I := 0 to ControlCount - 1 do
11      begin
12        fld := Controls[i];
13        if (fld is TDBEdit) then
14        begin
15          fldEmpty := TDBEdit(fld).GetTextLen = 0;
16          if fldEmpty then
17            Break;
18        end
19      end;
20      AddfrmNextBtn.Enabled := not fldEmpty;
21    end;
22  end;
23  
24  if fldName is TCustomEdit then
25    fldEmpty := TCustomEdit(fldName).GetTextLen = 0;