CodeBehind Checkbox.Checked = false but boxes remain "visiably" checked, value is false though

I have a list of checkboxes on my asp.net web application that after the submit button is clicked, i am trying to loop threw each checkbox and set its value to false. The checkbox on the page remains with a checkmark still even though its value is false. What event or action needs to happen to make sure the checkbox visually represents its value.

If possible, I'm doing this is c# and I would really like to do this in codeBehind to understand why this is not working.

Thanks for any help