SendMessage的简单有关问题!

SendMessage的简单问题!!!
发送方
const
    WM_TEST   =   WM_USER   +   20;

procedure   TTbc.Button1Click(Sender:   TObject);
var
    a:   HWND;
begin
    a   :=   FindWindow( 'TTabc ',   nil);
    SendMessage(a,   WM_TEST,   100,   0);
end;

接收方:
const
    WM_TEST   =   WM_USER   +   20;

procedure   Test(var   Msg:   TMsg);message   WM_TEST;

procedure   TTabc.Test(var   Msg:   TMsg);
begin
    ShowMessage(Format( 'message:%d;     Wparam:%d;     Lparam:%d ',
        [Msg.message,   Msg.wParam,   Msg.lParam]));
nd;
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问题是我接收到的时候，为什么100是存放在Msg.message里了？而不是Msg.wParam
!但是当我SendMessage(a,   WM_TEST,   ０,   1000)时Msg.wParam就能收到，这好像和SendMessage的帮助里说的不同？？？



[解决办法]
不知道为什么。自定义消息是从wm_user+100开始的
[解决办法]
procedure TTabc.Test(var Msg: TMsg);
把这个改成
procedure TTabc.Test(var Msg: TMessage);

注意二者得区别
tagMSG = packed record
hwnd: HWND;
message: UINT;
wParam: WPARAM;
lParam: LPARAM;
time: DWORD;
pt: TPoint;
end;

TMessage = packed record
Msg: Cardinal;
case Integer of
0: (
WParam: Longint;
LParam: Longint;
Result: Longint);
1: (
WParamLo: Word;
WParamHi: Word;
LParamLo: Word;
LParamHi: Word;
ResultLo: Word;
ResultHi: Word);
end;
[解决办法]
用TMessage阿