C#在picturebox 中画的图，保存为dxf格式，谢谢
http://zhidao.baidu.com/link?url=3dkHwNhEfd1ADzIClIwsODab-O2-d4Hxy6wkJh0GBLbNd8tTCmCh0HhWDIYecFH0aLFkU7rsdnvBQ8qpnZxcMq