最近在做一个小画图程序，程序要用到两个不同消息的SendMessage，如果我按照注释中的方法，当然注释1和注释2的iButtonState 和 oButtonState要替代IF中的SendMessage
语句，可是那样空件就画不出线来，这是为什么？
LRESULT CALLBACK MainWndProc(HWND hWnd, UINT Msg,
                             WPARAM wParam, LPARAM lParam)
{

    HDC hDC;
    static BOOL IsDrawing = FALSE;
    static int StartX, StartY;
    static int EndX, EndY;
//    UINT iButtonState=0;
    //UINT oButtonState=0;

    
    switch(Msg)
    {
    case WM_CREATE:
        Exo.CreateStandardToolbar(hWnd, Exo.hInst);
        SendMessage(Exo.hWndToolbar, TB_SETSTATE, IDM_DRAW_ARROW, TBSTATE_CHECKED | TBSTATE_ENABLED);    
        
        return 0;

    case WM_ACTIVATE:
        Exo.Wnd.SetText("RainDrop - Untitled");
        return 0;

    case WM_LBUTTONDOWN:

        1//iButtonState = SendMessage(Exo.hWndToolbar, TB_GETSTATE, IDM_DRAW_LINE, 0);

        2//oButtonState = SendMessage(Exo.hWndToolbar, TB_GETSTATE, IDM_DRAW_FREEHAND, 0);


        if( SendMessage(Exo.hWndToolbar, TB_GETSTATE, IDM_DRAW_LINE, 0) & TBSTATE_CHECKED )
        {
            hDC = GetDC(hWnd);
            StartX = LOWORD(lParam);
            StartY = HIWORD(lParam);
        
            EndX = LOWORD(lParam);
            EndY = HIWORD(lParam);
        
            SetROP2(hDC, R2_XORPEN);

            MoveToEx(hDC, StartX, StartY, NULL);
            LineTo(hDC, EndX, EndY);
            IsDrawing = TRUE;
            ReleaseDC(hWnd, hDC);
        }
        else if(SendMessage(Exo.hWndToolbar, TB_GETSTATE, IDM_DRAW_FREEHAND, 0) & TBSTATE_CHECKED )
        {
            StartX = LOWORD(lParam);
            StartY = HIWORD(lParam);
            EndX = StartX;
            EndY = StartY;
            IsDrawing = TRUE;
        }

        return 0;