<div class="dropdown d-inline">
  <button class="btn btn-success dropdown-toggle" id="dropdownMenuButton" type="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">انتخاب شهر</button>
  <div class="dropdown-menu dropdown-menu-right" aria-labelledby="dropdownMenuButton">
      <a class="dropdown-item" href="#">کاشان</a>
      <a class="dropdown-item" href="#">تهران</a>
      <a class="dropdown-item" href="#">اصفهان</a></div>
</div>