BlazorFiddle - Blazor .Net Developer Playground and Code Editor in the Browser.

Index

@page "/"

   <div class="wrapper">
        <!-- Navbar -->
        <nav class="main-header navbar navbar-expand navbar-white navbar-light">
            <!-- Left navbar links -->
            <ul class="navbar-nav">
                <li class="nav-item">
                    <a class="nav-link" data-widget="pushmenu" href="#" role="button"><i class="fas fa-bars"></i></a>
                </li>
                <li class="nav-item d-none d-sm-inline-block">
                    <a href="index3.html" class="nav-link">Home</a>
                </li>
                <li class="nav-item d-none d-sm-inline-block">
                    <a href="#" class="nav-link">Contact</a>
                </li>
            </ul>

            <!-- Right navbar links -->
            <ul class="navbar-nav ml-auto">
                <!-- Navbar Search -->
                <li class="nav-item">
                    <a class="nav-link" data-widget="navbar-search" href="#" role="button">
                        <i class="fas fa-search"></i>
                    </a>
                    <div class="navbar-search-block">
                        <form class="form-inline">
                            <div class="input-group input-group-sm">
                                <input class="form-control form-control-navbar" type="search" placeholder="Search"
                                    aria-label="Search">
                                <div class="input-group-append">
                                    <button class="btn btn-navbar" type="submit">
                                        <i class="fas fa-search"></i>
                                    </button>
                                    <button class="btn btn-navbar" type="button" data-widget="navbar-search">
                                        <i class="fas fa-times"></i>
                                    </button>
                                </div>
                            </div>
                        </form>
                    </div>
                </li>

                <!-- Messages Dropdown Menu -->
                <li class="nav-item dropdown">
                    <a class="nav-link" data-toggle="dropdown" href="#">
                        <i class="far fa-comments"></i>
                        <span class="badge badge-danger navbar-badge">3</span>
                    </a>
                    <div class="dropdown-menu dropdown-menu-lg dropdown-menu-right">
                        <a href="#" class="dropdown-item">
                            <!-- Message Start -->
                            <div class="media">
                                <img src="https://adminlte.io/themes/v3/dist/img/user1-128x128.jpg" alt="User Avatar"
                                    class="img-size-50 mr-3 img-circle">
                                <div class="media-body">
                                    <h3 class="dropdown-item-title">
                                        Brad Diesel
                                        <span class="float-right text-sm text-danger"><i class="fas fa-star"></i></span>
                                    </h3>
                                    <p class="text-sm">Call me whenever you can...</p>
                                    <p class="text-sm text-muted"><i class="far fa-clock mr-1"></i> 4 Hours Ago</p>
                                </div>
                            </div>
                            <!-- Message End -->
                        </a>
                        <div class="dropdown-divider"></div>
                        <a href="#" class="dropdown-item">
                            <!-- Message Start -->
                            <div class="media">
                                <img src="https://adminlte.io/themes/v3/dist/img/user8-128x128.jpg" alt="User Avatar"
                                    class="img-size-50 img-circle mr-3">
                                <div class="media-body">
                                    <h3 class="dropdown-item-title">
                                        John Pierce
                                        <span class="float-right text-sm text-muted"><i class="fas fa-star"></i></span>
                                    </h3>
                                    <p class="text-sm">I got your message bro</p>
                                    <p class="text-sm text-muted"><i class="far fa-clock mr-1"></i> 4 Hours Ago</p>
                                </div>
                            </div>
                            <!-- Message End -->
                        </a>
                        <div class="dropdown-divider"></div>
                        <a href="#" class="dropdown-item">
                            <!-- Message Start -->
                            <div class="media">
                                <img src="https://adminlte.io/themes/v3/dist/img/user3-128x128.jpg" alt="User Avatar"
                                    class="img-size-50 img-circle mr-3">
                                <div class="media-body">
                                    <h3 class="dropdown-item-title">
                                        Nora Silvester
                                        <span class="float-right text-sm text-warning"><i
                                                class="fas fa-star"></i></span>
                                    </h3>
                                    <p class="text-sm">The subject goes here</p>
                                    <p class="text-sm text-muted"><i class="far fa-clock mr-1"></i> 4 Hours Ago</p>
                                </div>
                            </div>
                            <!-- Message End -->
                        </a>
                        <div class="dropdown-divider"></div>
                        <a href="#" class="dropdown-item dropdown-footer">See All Messages</a>
                    </div>
                </li>
                <!-- Notifications Dropdown Menu -->
                <li class="nav-item dropdown">
                    <a class="nav-link" data-toggle="dropdown" href="#">
                        <i class="far fa-bell"></i>
                        <span class="badge badge-warning navbar-badge">15</span>
                    </a>
                    <div class="dropdown-menu dropdown-menu-lg dropdown-menu-right">
                        <span class="dropdown-header">15 Notifications</span>
                        <div class="dropdown-divider"></div>
                        <a href="#" class="dropdown-item">
                            <i class="fas fa-envelope mr-2"></i> 4 new messages
                            <span class="float-right text-muted text-sm">3 mins</span>
                        </a>
                        <div class="dropdown-divider"></div>
                        <a href="#" class="dropdown-item">
                            <i class="fas fa-users mr-2"></i> 8 friend requests
                            <span class="float-right text-muted text-sm">12 hours</span>
                        </a>
                        <div class="dropdown-divider"></div>
                        <a href="#" class="dropdown-item">
                            <i class="fas fa-file mr-2"></i> 3 new reports
                            <span class="float-right text-muted text-sm">2 days</span>
                        </a>
                        <div class="dropdown-divider"></div>
                        <a href="#" class="dropdown-item dropdown-footer">See All Notifications</a>
                    </div>
                </li>
                <li class="nav-item">
                    <a class="nav-link" data-widget="fullscreen" href="#" role="button">
                        <i class="fas fa-expand-arrows-alt"></i>
                    </a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" data-widget="control-sidebar" data-slide="true" href="#" role="button">
                        <i class="fas fa-th-large"></i>
                    </a>
                </li>
            </ul>
        </nav>
        <!-- /.navbar -->

        <!-- Main Sidebar Container -->
        <aside class="main-sidebar sidebar-dark-primary elevation-4">
            <!-- Brand Logo -->
            <a href="index3.html" class="brand-link">
                <img src="https://adminlte.io/themes/v3/dist/img/AdminLTELogo.png" alt="AdminLTE Logo"
                    class="brand-image img-circle elevation-3" style="opacity: .8">
                <span class="brand-text font-weight-light">AdminLTE 3</span>
            </a>

            <!-- Sidebar -->
            <div class="sidebar">
                <!-- Sidebar user panel (optional) -->
                <div class="user-panel mt-3 pb-3 mb-3 d-flex">
                    <div class="image">
                        <img src="https://adminlte.io/themes/v3/dist/img/user2-160x160.jpg"
                            class="img-circle elevation-2" alt="User Image">
                    </div>
                    <div class="info">
                        <a href="#" class="d-block">Alexander Pierce</a>
                    </div>
                </div>

                <!-- SidebarSearch Form -->
                <div class="form-inline">
                    <div class="input-group" data-widget="sidebar-search">
                        <input class="form-control form-control-sidebar" type="search" placeholder="Search"
                            aria-label="Search">
                        <div class="input-group-append">
                            <button class="btn btn-sidebar">
                                <i class="fas fa-search fa-fw"></i>
                            </button>
                        </div>
                    </div>
                </div>

                <!-- Sidebar Menu -->
                <nav class="mt-2">
                    <ul class="nav nav-pills nav-sidebar flex-column" data-widget="treeview" role="menu"
                        data-accordion="false">
                        <!-- Add icons to the links using the .nav-icon class
               with font-awesome or any other icon font library -->
                        <li class="nav-item menu-open">
                            <a href="#" class="nav-link active">
                                <i class="nav-icon fas fa-tachometer-alt"></i>
                                <p>
                                    Starter Pages
                                    <i class="right fas fa-angle-left"></i>
                                </p>
                            </a>
                            <ul class="nav nav-treeview">
                                <li class="nav-item">
                                    <a href="#" class="nav-link active">
                                        <i class="far fa-circle nav-icon"></i>
                                        <p>Active Page</p>
                                    </a>
                                </li>
                                <li class="nav-item">
                                    <a href="#" class="nav-link">
                                        <i class="far fa-circle nav-icon"></i>
                                        <p>Inactive Page</p>
                                    </a>
                                </li>
                            </ul>
                        </li>
                        <li class="nav-item">
                            <a href="#" class="nav-link">
                                <i class="nav-icon fas fa-th"></i>
                                <p>
                                    Simple Link
                                    <span class="right badge badge-danger">New</span>
                                </p>
                            </a>
                        </li>
                    </ul>
                </nav>
                <!-- /.sidebar-menu -->
            </div>
            <!-- /.sidebar -->
        </aside>
    </div>

namespace BlazorFiddleProject
{
    using Microsoft.Extensions.DependencyInjection;


    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
        }

        // Warning: IComponentsApplicationBuilder - not the original .NET 6.0 interface. This was done to make old saves work. 
        public void Configure(IComponentsApplicationBuilder app)
        {
            app.AddComponent<App>("app");
        }
    }
}

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
    <meta name="viewport" content="width=device-width">
        <title>AdminLTE 3 | Starter</title>

    <!-- Google Font: Source Sans Pro -->
    <link rel="stylesheet"
        href="https://fonts.googleapis.com/css?family=Source+Sans+Pro:300,400,400i,700&display=fallback">
    <!-- Font Awesome Icons -->
    <link rel="stylesheet" href="https://adminlte.io/themes/v3/plugins/fontawesome-free/css/all.min.css">
    <!-- Theme style -->
    <link rel="stylesheet" href="https://adminlte.io/themes/v3/dist/css/adminlte.min.css">
    <script src="_content/MatBlazor/dist/matBlazor.js"></script>    
</head>
<body class="hold-transition sidebar-min">
<app>Loading...</app>

<script src="_framework/blazor.webassembly.js"></script>
    <!-- jQuery -->
<script src="https://adminlte.io/themes/v3/plugins/jquery/jquery.min.js"></script>
    <!-- Bootstrap 4 -->
<script src="https://adminlte.io/themes/v3/plugins/bootstrap/js/bootstrap.bundle.min.js"></script>
                <!-- AdminLTE App -->
<script src="https://adminlte.io/themes/v3/dist/js/adminlte.min.js"></script></body>
</html>

BlazorFiddle was updated from Blazor 0.7 to .NET 6.0. Your old source code could not work. You need to upgrade to latest.