文件问题

Question

unit filesystem;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    OpenDialog1: TOpenDialog;
    SaveDialog1: TSaveDialog;
    procedure Button4Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.Button4Click(Sender: TObject);   //exit
begin
        close;
end;procedure TForm1.Button1Click(Sender: TObject);  //new
begin
memo1.Lines.Add('在末端添加文本');
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
memo1.Lines.Text:='new file!';
end;procedure TForm1.Button2Click(Sender: TObject);   //打开和保存都要手动写入后缀.txt,这样才能自动保存为选定格式？
begin
if Opendialog1.Execute then
memo1.Lines.LoadFromFile(opendialog1.FileName);
end;procedure TForm1.Button3Click(Sender: TObject); //save
begin
if savedialog1.Execute then
memo1.Lines.SaveToFile(savedialog1.FileName);
end;
end.

Answer 1

设置 savedialog1 的 Filter 属性