以下示範如何利用 LPARAM 傳遞指標

Ex1: 傳遞整數指標

發送端:
var
  Num: integer;
begin
  Num := 0;
  SendMessage(Form1.Handle, WM_USER+100, 1, LPARAM(@Num));
  ShowMessage('Num = ' + IntToStr(Num));
end;

接收端:
procedure TForm1.OnUserMsg(var Message: TMessage);
var
  pi: ^integer;  // pi 是一個指向整數的指標
begin
  if Message.WParam = 1 then
  begin
    pi := pointer(Message.LParam);
    pi^ := 100;
  end;
end;