>>876 WM_GETTEXT版

procedure TForm1.Button1Click(Sender: TObject);
var
hEdit:HWND;
len:integer;
s:string;
begin
hEdit := GetWindow(FindWindow('Notepad',nil),GW_CHILD);
if hEdit = 0 then exit;
len := SendMessage(hEdit,WM_GETTEXTLENGTH,0,0);
SetLength(s,len+1);
SendMessage(hEdit,WM_GETTEXT,len+1,LPARAM(PChar(s)));
Memo1.Text := s;
end;