Procedure CreateParams(var Params :TCreateParams);override;

      inherited  CreateParams(Params);
      if    BorderStyle    =    bsNone    then
      with    Params    do
           Style := Style or WS_THICKFRAME;

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
  private
    { Private declarations }
  public
    { Public declarations }
    (*在public中加上这句*)
    Procedure CreateParams(var Params :TCreateParams);override;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TForm1 }

{*当窗口是无边框无标题的时候 显示边框   让窗体可拉伸*}
procedure TForm1.CreateParams(var Params: TCreateParams);
begin
  inherited;
  inherited  CreateParams(Params);
      if    BorderStyle    =    bsNone    then
      with    Params    do
           Style := Style or WS_THICKFRAME;
end;

end.