在 ASP.Net Core Web 应用程序（引导程序）中向 NavBar 添加下拉菜单

Question

In Visual Studio, I create a new ASP.Net Core Web App

then I add a dropdown menu (as per Bootstrap documentation) https://getbootstrap.com/docs/5.1/components/navbar/

the header porton of the html code looks like this:

<header>
    <nav class="navbar navbar-expand-sm navbar-toggleable-sm navbar-light bg-white border-bottom box-shadow mb-3">
        <div class="container">
            <a class="navbar-brand" asp-area="" asp-page="/Index">WebApplication1</a>
            <button class="navbar-toggler" type="button" data-toggle="collapse" data-target=".navbar-collapse" aria-controls="navbarSupportedContent"
                    aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>
            <div class="navbar-collapse collapse d-sm-inline-flex flex-sm-row-reverse">
                <ul class="navbar-nav flex-grow-1">
                    <li class="nav-item">
                        <a class="nav-link text-dark" asp-area="" asp-page="/Index">Home</a>
                    </li>
                    <li class="nav-item">
                        <a class="nav-link text-dark" asp-area="" asp-page="/Privacy">Privacy</a>
                    </li>
                    <li class="nav-item dropdown">
                      <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-bs-toggle="dropdown" aria-expanded="false">
                        Dropdown
                      </a>
                      <ul class="dropdown-menu" aria-labelledby="navbarDropdown">
                        <li><a class="dropdown-item" href="#">Action</a></li>
                        <li><a class="dropdown-item" href="#">Another action</a></li>
                        <li><hr class="dropdown-divider"></li>
                        <li><a class="dropdown-item" href="#">Something else here</a></li>
                      </ul>
                    </li>
                </ul>
            </div>
        </div>
    </nav>
</header>

but the dropdown doesn't work. When I click it, no dropdown appears: https://i.stack.imgur.com/szrE4.png

Answer 1

Be sure your Bootstrap version is v5.1 , you can add the following css and js file to your project _Layout.cshtml :

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.1.1/css/bootstrap.min.css" integrity="sha512-6KY5s6UI5J7SVYuZB4S/CZMyPylqyyNZco376NM2Z8Sb8OxEdp02e1jkKk/wZxIEmjQ6DRCEBhni+gpr9c4tvA==" crossorigin="anonymous" referrerpolicy="no-referrer" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.1.1/js/bootstrap.min.js" integrity="sha512-ewfXo9Gq53e1q1+WDTjaHAGZ8UvCWq0eXONhwDuIoaH8xz2r96uoAYaQCm1oQhnBfRXrvJztNXFsTloJfgbL5Q==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

For Bootstrap v4.x , you need change your code to:

<li class="nav-item dropdown">
        <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
            Dropdown
        </a>
        <div class="dropdown-menu" aria-labelledby="navbarDropdown">
            <a class="dropdown-item" href="#">Action</a>
            <a class="dropdown-item" href="#">Another action</a>
            <div class="dropdown-divider"></div>
            <a class="dropdown-item" href="#">Something else here</a>
        </div>
</li>

Answer 2

In Bootstrap 5.1, for dropdown,

✅ data-bs-toggle="dropdown"

❌data-toggle="dropdown"

In Bootstrap 4.0, for dropdown,

✅ data-toggle="dropdown"

❌data-bs-toggle="dropdown"