写了一个继承于Tpanel对象的控件，想在上面加一个Label,如何实现,详情请看里面。。。(100分)

写了一个继承于Tpanel对象的控件，可以通过自己的方法addlabel增加一个Label,编译通过,
但在使用时通过Mypanel1.addlabel方法时出错,并且不能显示Label,请各位大哥帮忙,我只是一个
爱好Delphi编程的人而已,难的问题我就解决不了，谢谢各位了
代码如下：
unit MyPanel;

interface

uses
Windows, Messages, SysUtils, Classes, Controls, ExtCtrls,StdCtrls;

type
TMyPanel = class(TPanel)
private
lb:Tlabel;
{ Private declarations }
protected
{ Protected declarations }
public
procedure addLabel;
constructor create(Aowner:Tcomponent);override;
destructor destroy;override;
{ Public declarations }
published
{ Published declarations }
end;

procedure Register;

implementation

procedure TMypanel.addLabel ;
begin
if not assigned(lb) then
begin
lb.Create(self); //以本控件为容器创建lb
lb.Caption :='hello';
lb.Left :=10;
lb.Top:=10;
lb.Invalidate ;
end;
end;
constructor tMypanel.create(Aowner:Tcomponent);
begin
inherited create(Aowner);
end;
destructor tMypanel.destroy ;
begin
if Assigned(lb) then
lb.free;
inherited destroy;
end;
procedure Register;
begin
RegisterComponents('ActiveX', [TMyPanel]);
end;

end.

procedure TMypanel.addLabel ;
begin
if not assigned(lb) then
begin
lb:= tlabel.Create(self);
lb.Parent := self;
lb.Caption :='hello';
lb.Left :=5;
lb.Top:=5;
lb.Invalidate ;
end;
end;

谢谢你了