How can I do an if statement based on option value? [Liquid / Shopify]

How can I run an if statement using liquid in Shopify based on the value of an option in a dropdown?

This is my code for the dropdown that I want to extract the information from:

<div class="grid__item large--one-half"> 
  <label for="ContactFormAddressSame" class="">contact.form.addressSame</label>
  <select id="ContactFormAddressSame" name="contact[addressSame]">
    <option>Yes</option>
    <option>No</option>
  </select>
</div>

Basically what I want to happen is if the value is equal to 'No' then do something. If 'Yes', don't do anything.