轉載地址：http://www.cnblogs.com/magic-cube/archive/2011/04/27/2029913.html
首先看看定義：
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typedef unsignedint UINT;typedef UINT WPARAM;//就是無符號整形typedef long LONG;typedef LONG LPARAM;//就是長整形 |
這就是所謂的wparam和lparam，從定義我們可以看出lparam比wparam要長，所以習慣上都用wparam來存儲消息類型，而用lparam來存儲要傳遞的參數，當然它的類型隨着消息的不同而變化：如發送一個WM_LBUTTONDOWN消息，
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SendMessage針對鼠標消息中wParam和lParam參數SendMessage(Hwnd,
WM_LBUTTONDOWN, wparam, lparam);SendMessage(Hwnd,
WM_LBUTTONUP, wparam, lparam); wParam //消息類型 MK_CONTROL
Set if the
ctrl key is down. MK_LBUTTON
Set if the
left mouse button is down. MK_MBUTTON
Set if the
middle mouse button is down. MK_RBUTTON
Set if the
right mouse button is down. MK_SHIFT
Set if the
shift key is down. lParam //傳遞參數xPos
= LOWORD(lParam); //horizontal
position of cursor yPos
= HIWORD(lParam); //vertical
position of cursor |