如果未选中列表中的一个，如何取消选中复选框？

I am trying a check a checkbox (which checks all other checkboxes in the list and unchecks even if one among the list is unchecked. Now only the first I mean one checkbox checking all the remaining checkboxes in the list is happening but the vice versa I mean unchecking even if one among the list in unchecked is not working. How can i achieve that?I am trying a check a checkbox (which checks al