<script src="~/Scripts/jquery-2.2.4.min.js"></script>
<script src="~/Scripts/bootstrap.min.js"></script>
<link href="~/Content/bootstrap.min.css" rel="stylesheet" />

<div class="dropdown">
    <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
        下拉菜单<span class="caret"></span>
    </button>
    <ul class="dropdown-menu">
        <li><a href="#">菜单项1</a></li>
        <li><a href="#">菜单项2</a></li>
        <li><a href="#">菜单项3</a></li>
    </ul>
</div>