在回调函数中使用with结构导致界面无响应

Delphi(Pascal) code

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls;type  TForm1 = class(TForm)    lst1: TListBox;    btn1: TButton;    procedure btn1Click(Sender: TObject);  private    { Private declarations }  public    { Public declarations }  end;  function GetTitle(Hwnd: THandle; Param: Pointer): Boolean; stdcall;var  Form1: TForm1;implementation{$R *.dfm}                                                                    function GetTitle(Hwnd: THandle; Param: Pointer): Boolean; stdcall; var                                                                   Text: String;                                                     begin                                                                 SetLength(Text, 100);  GetWindowText(Hwnd, PChar(Text), 100);  Text := PChar(Text);  if Text <> '' then  begin    //=============================问题代码=====================================    //用With结构会导致界面死掉    with Form1.lst1.Items do    begin      Add(IntToStr(Hwnd) + ':' + Text);    end;    //=============================问题代码=====================================    //正常    Form1.lst1.Items.Add(IntToStr(Hwnd) + ':' + Text);  end;  Result := True;end;procedure TForm1.btn1Click(Sender: TObject);var  EWProc: TFNWndEnumProc;begin  EWProc := @GetTitle;  EnumWindows (EWProc, 0);end;end.

问题描述：在回调函数中使用With结构导致程序界面无响应，不使用的话，一切正常
开发平台: Delphi 7 + Win7
问题：难道回调函数中还有什么限制么？


[解决办法]
with Form1.lst1.Items do
begin
Add(IntToStr(Hwnd) + ':' + Text);
end;

with中的Text实际上是Form1.lst1.Items.Text，即function TStrings.GetTextStr: string;
此函数中有两个for循环,都遍历了ListBox中的所有条目，调用Get逐一取了每个条目的内容，其中Get是
function TListBoxStrings.Get(Index: Integer): string;
此函数中调用两次SendMessage，先后发送LB_GETTEXTLEN和LB_GETTEXT!