两种方式：
1. 模拟键盘按键：
keybd_event(VK_CONTROL,0,0,0); //ctrl键按下
keybd_event(BYTE('C'),0,0,0); //c键按下
keybd_event(BYTE('C'),0,KEYEVENTF_KEYUP,0); //c键抬起
keybd_event(VK_CONTROL,0,KEYEVENTF_KEYUP,0); //ctrl键抬起
2. 向窗口发送WM_COPY消息
::SendMessage(::GetForegroundWindow(), WM_COPY, 0,0); //GetForegroundWindow() 获得当前活动窗口
