Net validating checkbox
The class automatically adds client-side script for handling the plumbing of client-side validation: performing validation when the form submits, determining what client-side function to invoke for validating each validator, and so on.
To add client-side functionality, however, we must add a bit more code.
property is set to true, all validation controls on the page that are not assigned to a validation group are validated when the control posts back to the server.
This property cannot be set by themes or style sheet themes.
When the button is clicked, we first count the checkboxes that are checked using $(':checkbox:checked').length .
If the length is 0 (zero), we alert the user and prevent the user from submitting the form using e.prevent Default().