title: How to get the total checked checkbox in a single column of gridview and show it into a label
body: <p>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).</p>
  
  <ol>
  <li>I want only one checkbox should be checked in a row.</li>
  <li>I want to show the total present student(means total of "present checkbox" column checked checkboxes) in a label names total present students.</li>
  </ol>
  
  <p>Any Suggestion would be appreciated.  <a href="http://i.stack.imgur.com/bahu8.png" rel="nofollow">GridView ScreenShot</a></p>