How to get the total checked checkbox in a single column of gridview and show it into a label

I need some help. I searched mostly sites but did not find desired code for my query. I am coding for a module of "Attendance of Class" in window application and here I have a gridview having student name(textbox column), roll no(textbox column), present(checkbox column), absent(checkbox column), on leave(checkbox column). 1) I want only one checkbox should be checked in a row. 2) I want to show the total present student(means total of "present checkbox" column checked checkboxes) in a label names total present students.

Any Suggestion would be appreciated. Thanks in advance GridView ScreenShot