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//普通VC++获取客户区设备句柄
HDC hdc;
hdc=::GetDC(m_hWnd);
MoveToEx(hdc,m_point.x,m_point.y,NULL);
LineTo(hdc,point.x,point.y);
//MFC封装类获取客户区设备句柄，需要ReleaseDC
CDC *cdc = GetDC();
cdc->MoveTo(m_point);
cdc->LineTo(point);
ReleaseDC(cdc);
//CDC继承类CClientDC，析构自动释放Release
CClientDC dc(this);
dc.MoveTo(m_point);
dc.LineTo(point);
//CDC继承类CWindowDC
CWindowDC dc(this);
dc.MoveTo(m_point);
dc.LineTo(point);
CWnd::GetParent --- 获取父窗口指针
CWnd::GetDesktopWindow() --- 获取桌面指针
静态 static
静态方法中不能调用非静态成员变量或成员函数
非静态方法中可以调用静态成员
静态方法中静态成员变量调用前必须初始化