我怎么收不到自定义的消息

[土豆薯条]

*.h
#define WM_NC1_NOTIFY (WM_USER + 1)
class TForm1 : public TForm
{
__published: // IDE-managed Components
TButton *Button1;
void __fastcall WMNCNotify(TMessage &Msg);
private: // User declarations
BEGIN_MESSAGE_MAP
VCL_MESSAGE_HANDLER(WM_NC1_NOTIFY, TMessage, WMNCNotify)
END_MESSAGE_MAP(TForm)
public: // User declarations
__fastcall TForm1(TComponent* Owner);
};
*.cpp
void __fastcall TForm1::WMNCNotify(TMessage& Msg)
{
POINT MousePos;
switch(Msg.LParam)
{

case WM_LBUTTONDOWN:
Show();
break;
default:
break;
}
TForm::Dispatch(&Msg);
}
我在switch(Msg.LParam)处设置断点，程序怎么没进来？？