select and unselect row in grid

Question

Hello, people,

I'm new to windows forms and stuck with row selection. If user is selecting row for the first time, it should select. If user selects the same row again, it should automatically got unselected. how can i do this. Single selction, i am able to do but I'm not abel to unselect. need urgent help. I m using listview_ItemSelectionChanged event, which is inbuilt.