datagridview怎么获取当前选中行的索引值

datagridview怎么获取当前选中行的索引值，和当前选中单元格的行索引值

dgv.CurrentCell.RowIndex;

http://blog.csdn.net/a316019667/article/details/6697047
http://blog.csdn.net/andrew_wx/article/details/6546979