Saving listbox items questions

unit3.dfm:
object Form3: TForm3
  Left = 0
  Top = 0
  Caption = 'Form3'
  ClientHeight = 247
  ClientWidth = 354
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  PixelsPerInch = 96
  TextHeight = 13
  object lbLines: TListBox
    Left = 8
    Top = 16
    Width = 121
    Height = 201
    ItemHeight = 13
    MultiSelect = True
    TabOrder = 0
  end
  object btnAdd: TButton
    Left = 136
    Top = 16
    Width = 75
    Height = 25
    Caption = 'btnAdd'
    TabOrder = 1
    OnClick = btnAddClick
  end
  object btnDelete: TButton
    Left = 136
    Top = 48
    Width = 75
    Height = 25
    Caption = 'btnDelete'
    TabOrder = 2
    OnClick = btnDeleteClick
  end
  object btnLoad: TButton
    Left = 272
    Top = 48
    Width = 75
    Height = 25
    Caption = 'btnLoad'
    TabOrder = 3
    OnClick = btnLoadClick
  end
  object btnSave: TButton
    Left = 272
    Top = 80
    Width = 75
    Height = 25
    Caption = 'btnSave'
    TabOrder = 4
    OnClick = btnSaveClick
  end
  object btnNew: TButton
    Left = 272
    Top = 16
    Width = 75
    Height = 25
    Caption = 'btnNew'
    TabOrder = 5
    OnClick = btnNewClick
  end
  object btnSaveAs: TButton
    Left = 272
    Top = 112
    Width = 75
    Height = 25
    Caption = 'btnSaveAs'
    TabOrder = 6
    OnClick = btnSaveAsClick
  end
  object OpenDialog1: TOpenDialog
    DefaultExt = 'txt'
    Filter = 'text File|*.txt'
    Left = 192
    Top = 24
  end
  object SaveDialog1: TSaveDialog
    DefaultExt = 'txt'
    Filter = 'text File|*.txt'
    Left = 232
    Top = 24
  end
  object ApplicationEvents1: TApplicationEvents
    OnIdle = ApplicationEvents1Idle
    Left = 168
    Top = 104
  end
end
 
Unit3.pas:
unit Unit3;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, AppEvnts, StdCtrls;
 
const
  CFILENAMENEW = 'unsaved.txt';
 
type
  TForm3 = class(TForm)
    lbLines: TListBox;
    OpenDialog1: TOpenDialog;
    SaveDialog1: TSaveDialog;
    btnAdd: TButton;
    btnDelete: TButton;
    ApplicationEvents1: TApplicationEvents;
    btnLoad: TButton;
    btnSave: TButton;
    btnNew: TButton;
    btnSaveAs: TButton;
    procedure btnAddClick(Sender: TObject);
    procedure btnDeleteClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure btnNewClick(Sender: TObject);
    procedure btnSaveClick(Sender: TObject);
    procedure btnLoadClick(Sender: TObject);
    procedure ApplicationEvents1Idle(Sender: TObject; var Done: Boolean);
    procedure btnSaveAsClick(Sender: TObject);
  private
    FLinesModified: boolean;
    FLinesFileName: string;
    procedure SetLinesModified(const Value: boolean);
    procedure SetLinesFileName(const Value: string);
    { Private declarations }
  public
    { Public declarations }
    procedure DoLoadFile;
    procedure DoNewFile;
    procedure DoSaveFile;
    procedure DoSaveFileAs;
    procedure SetCaptionWithFileName;
    property LinesModified: boolean read FLinesModified write SetLinesModified;
    property LinesFileName: string read FLinesFileName write SetLinesFileName;
  end;
 
var
  Form3: TForm3;
 
implementation
 
{$R *.dfm}
 
{ TForm3 }
 
procedure TForm3.ApplicationEvents1Idle(Sender: TObject; var Done: Boolean);
begin
  btnDelete.Enabled := lbLines.SelCount > 0;
end;
 
procedure TForm3.btnAddClick(Sender: TObject);
begin
  lbLines.Items.Add(TimeToStr(Now));
  LinesModified := True;
end;
 
procedure TForm3.btnDeleteClick(Sender: TObject);
var
  i: integer;
begin
  i := 0;
  while lbLines.SelCount > 0 do begin
    if lbLines.Selected[i] then begin
      lbLines.Items.Delete(i);
      LinesModified := True;
    end else
      inc(i);
  end;
end;
 
procedure TForm3.btnLoadClick(Sender: TObject);
begin
  DoLoadFile;
end;
 
procedure TForm3.btnNewClick(Sender: TObject);
begin
  if LinesModified then
    DoSaveFile;
  DoNewFile;
end;
 
procedure TForm3.btnSaveAsClick(Sender: TObject);
begin
  DoSaveFileAs;
end;
 
procedure TForm3.btnSaveClick(Sender: TObject);
begin
  DoSaveFile;
end;
 
procedure TForm3.DoLoadFile;
begin
  if LinesModified then
    DoSaveFile;
 
  if OpenDialog1.Execute then begin
    lbLines.Items.LoadFromFile(OpenDialog1.FileName);
    LinesFileName := OpenDialog1.FileName;
    LinesModified := False;
  end;
end;
 
procedure TForm3.DoNewFile;
begin
  lbLines.Clear;
  FLinesModified := False;
  FLinesFileName := CFILENAMENEW;
  SetCaptionWithFileName;
end;
 
procedure TForm3.DoSaveFile;
var
  strFileName: string;
begin
  strFileName := ExtractFileName(LinesFileName);
  case MessageDlg(Format('Do you want to save %s?', [strFileName]), mtConfirmation, [mbYes, mbNo], 0) of
    mrNo: Exit;
    mrCancel: Exit;
  end;
  if strFileName = CFILENAMENEW then begin
    if SaveDialog1.Execute then begin
      LinesFileName := SaveDialog1.FileName;
    end else
      Exit;
  end;
  lbLines.Items.SaveToFile(LinesFileName);
  LinesModified := False;
end;
 
procedure TForm3.DoSaveFileAs;
begin
  if SaveDialog1.Execute then begin
    LinesFileName := SaveDialog1.FileName;
    lbLines.Items.SaveToFile(LinesFileName);
    LinesModified := False;
  end;
end;
 
procedure TForm3.FormCreate(Sender: TObject);
begin
  DoNewFile;
end;
 
procedure TForm3.SetCaptionWithFileName;
var
  strModifiedStar: string;
begin
  if LinesModified then
    strModifiedStar := '*'
  else
    strModifiedStar := '';
  Caption := Format('%s%s - %s ', [ExtractFileName(FLinesFileName), strModifiedStar, Application.Title]);
end;
 
procedure TForm3.SetLinesFileName(const Value: string);
begin
  if FLinesFileName <> Value then begin
    FLinesFileName := Value;
    SetCaptionWithFileName;
  end;
end;
 
procedure TForm3.SetLinesModified(const Value: boolean);
begin
  if FLinesModified <> Value then begin
    FLinesModified := Value;
    SetCaptionWithFileName;
  end;
end;
 
end.
                                              

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