int test_width(TObject *Obj)
{
  return Obj->Width;
}

  //.cpp內容
  void __fastcall TForm1::Button1Click(TObject *Sender)
  {
    Show(Image1);
  }
  //---------------------------------------------------------------------------
  void __fastcall TForm1::Show(TImage *img)
  {
    ShowMessage(AnsiString (img->Width));
  }      //.h內容
  //---------------------------------------------------------------------------
  class TForm1 : public TForm
  {
    __published:        // IDE-managed Components
        TButton *Button1;
        TImage *Image1;
        void __fastcall Button1Click(TObject *Sender);
        void __fastcall Show(TImage *img);
    private:        // User declarations
    public:                // User declarations
        __fastcall TForm1(TComponent* Owner);
  };

int test_width(TObject *Obj)
{
  return dynamic_cast(Obj)->Width;
}