导航栏里我加了下拉菜单，如果</nav>后不加内容，下拉菜单正常显示，如果加了其它内容，无法显示下拉菜单。看了很多回答，我的jquery和bootstrap引入顺序应该没问题，真心求解
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>@ViewData["Title"] - Photo_Call</title>
<!-- <link rel="stylesheet" href="~/lib/bootstrap/dist/css/bootstrap.min.css" /> -->
<link rel="stylesheet" href="~/css/site.css" />
<link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/css/bootstrap.min.css">
<script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script>
<script src="https://cdn.staticfile.org/popper.js/1.15.0/umd/popper.min.js"></script>
<script src="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/js/bootstrap.min.js"></script>
</head>
<body>
<header>
<nav class="navbar navbar-default navbar-expand-sm navbar-toggleable-sm navbar-dark bg-dark border-bottom box-shadow mb-3 fixed-top">
<div class="container" style="overflow:visible;">
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbar-collapse">
<span class="navbar-toggler-icon"></span>
</button>
<a class="navbar-brand" asp-area="" asp-page="/Index">
<img src="~/img/Logo.png" alt="icon" style="width:40px;"/>
</a>
<div class="navbar-collapse collapse d-sm-inline-flex flex-sm-row-reverse" id="navbar-collapse" style="overflow:visible;">
<ul class="navbar-nav flex-grow-1 nav-justified justify-content-center">
<li class="nav-item">
<a class="nav-link text-light" asp-area="" asp-page="/Index">Home</a>
</li>
<li class="nav-item">
<a class="nav-link text-light" asp-area="" asp-page="/Index">Order</a>
</li>
<li class="nav-item">
<a class="nav-link text-light" asp-area="" asp-page="/Index">Forum</a>
</li>
<li class="nav-item dropdown open">
<a class="nav-link text-light dropdown-toggle" id="navbardrop" data-toggle="dropdown">
Mine
</a>
<div class="dropdown-menu bg-dark border-bottom" style="text-align:center;">
<a class="dropdown-item text-light" asp-area="" asp-page="">Display</a>
<a class="dropdown-item text-light" asp-area="" asp-page="">Account</a>
</div>
</li>
<li class="nav-item dropdown">
<a class="nav-link text-light dropdown-toggle" id="navbardrop" data-toggle="dropdown">
Support
<b class="caret"></b>
</a>
<div class="dropdown-menu bg-dark border-bottom" style="text-align:center;">
<a class="dropdown-item text-light" asp-area="" asp-page="/Contact_Us.cshtml">Contact Us</a>
<a class="dropdown-item text-light" asp-area="" asp-page="">Privacy</a>
</div>
</li>
<li class="nav-item dropdown">
<div class="btn-group">
<button class="btn btn-primary dropdown-toggle" id="navbardrop" data-toggle="dropdown">
Sign In
</button>
<div class="dropdown-menu bg-dark border-bottom text-light" style="text-align:center;">
<form>
<div class="form-group">
<label for="email">Email address:</label>
<input type="email" class="form-control" id="account">
</div>
<div class="form-group">
<label for="pwd">Password:</label>
<input type="password" class="form-control" id="pwd">
</div>
<button type="submit" class="btn btn-primary justify-content-center">
Submit
</button>
</form>
</div>
<button type="button" class="btn btn-primary">Register</button>
</div>
</li>
</ul>
</div>
</div>
</nav>
</header>
<div class="container">
<main role="main" class="pb-3">
@RenderBody()
</main>
</div>
<footer class="border-top footer text-muted">
<div class="container">
© 2021 - Photo_Call - <a asp-area="" asp-page="/Privacy">Privacy</a>
</div>
</footer>
<script src="~/lib/jquery/dist/jquery.min.js"></script>
<script src="~/lib/bootstrap/dist/js/bootstrap.bundle.min.js"></script>
<script src="~/js/site.js" asp-append-version="true"></script>
@RenderSection("Scripts", required: false)
</body>
</html>
如果猜的没错的话应该是样式挤到一起去了，检查元素，调整一下位置大小