最简单得办法，用经典Pascal的Read，Write就可以，

用 win32中的richedit 控件就可以了，他的属性里面基本都全了。

呵呵，楼主的问题问得太泛。首先要确定你要实现什么样的文本文件操作先，对于不同的操作有很多可以选择的实现方法。

 编程实现文件预览

————————————————以下为程序代码—————————————


TXTDLGTEMPLATE DIALOG 0, 0, 316, 76
STYLE 0x404L | WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS
FONT 8, "MS Sans Serif"
{
    LTEXT "", 1119, 0, 0, 204, 76, SS_LEFT | WS_CHILD | NOT WS_VISIBLE | WS_GROUP
}


————————————————————————————————

unit txtDialog;

interface

uses
  Windows, Messages, SysUtils, Classes, StdCtrls, ExtCtrls, Buttons,
  Dialogs, ShellAPI, Controls;
  
type
  TtxtDialog = class(TOpenDialog)
  private
    { Private declarations }
    FtxtPanel: TPanel;
    FtxtLabel: TLabel;
    FPreviewButton: TSpeedButton;
    FtxtCtrl: TMemo;
  protected
    { Protected declarations }
    procedure PreviewClick(Sender: TObject); virtual;
    procedure DoSelectionChange; override;
    procedure DoShow; override;
    property txtCtrl: TMemo read FtxtCtrl;
  public
    { Public declarations }
    constructor Create(AOwner: TComponent); override;
    function Execute: Boolean; override;
  published
    { Published declarations }
  end;

implementation

{$R txtDialog.res}

{ TtxtDialog }

constructor TtxtDialog.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  //文件扩展名过滤器
  Filter := '文本文件 (*.txt)|*.txt';
  //定义一个主Panel---FtxtPanel，其他所有的构件都建立在这个Panel上
  FtxtPanel := TPanel.Create(Self);
  with FtxtPanel do begin
    Name := 'txtPanel';
    Caption := '';
    SetBounds(204, 5, 169, 200);
    BevelOuter := bvNone;
    BorderWidth := 2;
    TabOrder := 1;
    FtxtLabel := TLabel.Create(Self);
    with FtxtLabel do begin
      Name := 'txtLabel';
      Caption := '文本文件预览';
      Font.Charset := GB2312_CHARSET;
      Font.Name := '宋体';
      Font.Size := 9;
      SetBounds(6, 6, 157, 23);
      Align := alTop;
      AutoSize := False;
      Parent := FtxtPanel;
    end;
    //文件预览按钮
    FPreviewButton := TSpeedButton.Create(Self);
    with FPreviewButton do begin
      Name := 'PreviewButton';
      SetBounds(77, 1, 23, 22);
      Enabled := False;
      //从资源文件中读出TXTGLYPH图像，用于SpeedButton的图像
      Glyph.LoadFromResourceName(HInstance, 'TXTGLYPH');
      Hint := '查看该文件';
      ParentShowHint := False;
      ShowHint := True;
      //OnClick事件，调用记事本打开该文本文件
      OnClick := PreviewClick;
      Parent := FtxtPanel;
    end;
    //添加一个Memo元件，用于显示文件内容
    FtxtCtrl := TMemo.Create(Self);
    with FtxtCtrl do begin
      Name := 'Memo';
      SetBounds(6, 29, 157, 145);
      Align:=alClient;
      //OnDblClick事件
      OnDblClick := PreviewClick;
      TabOrder := 2;
      ReadOnly:=True;
      Text:='';
      ScrollBars:=ssBoth;
      Parent := FtxtPanel;
    end;
  end;
end;

procedure TtxtDialog.DoSelectionChange;
var
  Valided: Boolean;
  f : TextFile;
  s : string;

  function ValidFile(const FileName: string): Boolean;
  begin
    Result := GetFileAttributes(PChar(FileName)) <> $FFFFFFFF;
  end;
begin
  FtxtCtrl.Lines.Clear;
  Valided := FileExists(FileName) and
             ValidFile(FileName) and
             (UpperCase(ExtractFileExt(Filename))='.TXT');
  if Valided then
  try
    //打开文件，逐行读入Memo的Lines，完成预览
    AssignFile(f,Filename);
    FileMode:=fmOpenRead;
    Reset(f);
    while not EOF(f) do begin
      Readln(f,s);
      FtxtCtrl.Lines.Add(s);
    end;
    CloseFile(f);
    FPreviewButton.Enabled := True;
  except
    Valided := False;
  end;
  if not Valided then
    FPreviewButton.Enabled := False;
  inherited DoSelectionChange;
end;

procedure TtxtDialog.DoShow;
var
  PreviewRect, StaticRect: TRect;
begin
  //GetClientRect是Windows API，求出了整个Client区的大小
  GetClientRect(Handle, PreviewRect);
  //GetStaticRect是TOpenDialog提供的方法，求出了标准区的大小
  StaticRect := GetStaticRect;
  //将PreviewRect缩小在StaticRect的右边
  //应该使用PreviewRect.Left := StaticRect.Right，此处保留了ExtDlgs.pas中语句
  PreviewRect.Left := StaticRect.Left + (StaticRect.Right - StaticRect.Left);
  Inc(PreviewRect.Top, 4);
  //添加预览内容
  FtxtPanel.BoundsRect := PreviewRect;
  FPreviewButton.Left := FtxtCtrl.BoundsRect.Right - FPreviewButton.Width - 2;
  FtxtPanel.ParentWindow := Handle;
  inherited DoShow;
end;

function TtxtDialog.Execute: Boolean;
begin
  //传递自定义对话框TXTDLGTEMPLATE
  if NewStyleControls and not (ofOldStyleDialog in Options) then
    Template := 'TXTDLGTEMPLATE'
  else
    Template := nil;
  Result := inherited Execute;
end;

procedure TtxtDialog.PreviewClick(Sender: TObject);
begin
  //使用记事本打开该文本文件
  if UpperCase(ExtractFileExt(Filename))='.TXT' then
    ShellExecute(Application.Handle,'open',PChar(Filename),'','',SW_SHOW);
end;

end.


————————————————————————————————

var
  Demo : TtxtDialog;
begin
  Demo:=TtxtDialog.Create(Form1);
  Demo.Execute;
  Demo.Free;
end;

谢谢danlong.

谢谢danlong 。

很有用的代码啊，谢过了~~~~~~！