Add project files.

Lieb/Shared/MainLayout.razor

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+@inherits LayoutComponentBase
+
+<PageTitle>Lieb</PageTitle>
+
+<div class="page">
+    <div class="sidebar">
+        <NavMenu />
+    </div>
+
+    <main>
+        <div class="top-row px-4">
+            <a href="https://docs.microsoft.com/aspnet/" target="_blank">About</a>
+        </div>
+
+        <article class="content px-4">
+            @Body
+        </article>
+    </main>
+</div>

Lieb/Shared/MainLayout.razor.css

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+.page {
+    position: relative;
+    display: flex;
+    flex-direction: column;
+}
+
+main {
+    flex: 1;
+}
+
+.sidebar {
+    background-image: linear-gradient(180deg, rgb(5, 39, 103) 0%, #3a0647 70%);
+}
+
+.top-row {
+    background-color: #f7f7f7;
+    border-bottom: 1px solid #d6d5d5;
+    justify-content: flex-end;
+    height: 3.5rem;
+    display: flex;
+    align-items: center;
+}
+
+    .top-row ::deep a, .top-row .btn-link {
+        white-space: nowrap;
+        margin-left: 1.5rem;
+    }
+
+    .top-row a:first-child {
+        overflow: hidden;
+        text-overflow: ellipsis;
+    }
+
+@media (max-width: 640.98px) {
+    .top-row:not(.auth) {
+        display: none;
+    }
+
+    .top-row.auth {
+        justify-content: space-between;
+    }
+
+    .top-row a, .top-row .btn-link {
+        margin-left: 0;
+    }
+}
+
+@media (min-width: 641px) {
+    .page {
+        flex-direction: row;
+    }
+
+    .sidebar {
+        width: 250px;
+        height: 100vh;
+        position: sticky;
+        top: 0;
+    }
+
+    .top-row {
+        position: sticky;
+        top: 0;
+        z-index: 1;
+    }
+
+    .top-row, article {
+        padding-left: 2rem !important;
+        padding-right: 1.5rem !important;
+    }
+}

Lieb/Shared/NavMenu.razor

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+<div class="top-row ps-3 navbar navbar-dark">
+    <div class="container-fluid">
+        <a class="navbar-brand" href="">Lieb</a>
+        <button title="Navigation menu" class="navbar-toggler" @onclick="ToggleNavMenu">
+            <span class="navbar-toggler-icon"></span>
+        </button>
+    </div>
+</div>
+
+<div class="@NavMenuCssClass" @onclick="ToggleNavMenu">
+    <nav class="flex-column">
+        <div class="nav-item px-3">
+            <NavLink class="nav-link" href="" Match="NavLinkMatch.All">
+                <span class="oi oi-home" aria-hidden="true"></span> Home
+            </NavLink>
+        </div>
+        <div class="nav-item px-3">
+            <NavLink class="nav-link" href="counter">
+                <span class="oi oi-plus" aria-hidden="true"></span> Counter
+            </NavLink>
+        </div>
+        <div class="nav-item px-3">
+            <NavLink class="nav-link" href="fetchdata">
+                <span class="oi oi-list-rich" aria-hidden="true"></span> Fetch data
+            </NavLink>
+        </div>
+    </nav>
+</div>
+
+@code {
+    private bool collapseNavMenu = true;
+
+    private string? NavMenuCssClass => collapseNavMenu ? "collapse" : null;
+
+    private void ToggleNavMenu()
+    {
+        collapseNavMenu = !collapseNavMenu;
+    }
+}

Lieb/Shared/NavMenu.razor.css

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+.navbar-toggler {
+    background-color: rgba(255, 255, 255, 0.1);
+}
+
+.top-row {
+    height: 3.5rem;
+    background-color: rgba(0,0,0,0.4);
+}
+
+.navbar-brand {
+    font-size: 1.1rem;
+}
+
+.oi {
+    width: 2rem;
+    font-size: 1.1rem;
+    vertical-align: text-top;
+    top: -2px;
+}
+
+.nav-item {
+    font-size: 0.9rem;
+    padding-bottom: 0.5rem;
+}
+
+    .nav-item:first-of-type {
+        padding-top: 1rem;
+    }
+
+    .nav-item:last-of-type {
+        padding-bottom: 1rem;
+    }
+
+    .nav-item ::deep a {
+        color: #d7d7d7;
+        border-radius: 4px;
+        height: 3rem;
+        display: flex;
+        align-items: center;
+        line-height: 3rem;
+    }
+
+.nav-item ::deep a.active {
+    background-color: rgba(255,255,255,0.25);
+    color: white;
+}
+
+.nav-item ::deep a:hover {
+    background-color: rgba(255,255,255,0.1);
+    color: white;
+}
+
+@media (min-width: 641px) {
+    .navbar-toggler {
+        display: none;
+    }
+
+    .collapse {
+        /* Never collapse the sidebar for wide screens */
+        display: block;
+    }
+}

Lieb/Shared/SurveyPrompt.razor

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+<div class="alert alert-secondary mt-4">
+    <span class="oi oi-pencil me-2" aria-hidden="true"></span>
+    <strong>@Title</strong>
+
+    <span class="text-nowrap">
+        Please take our
+        <a target="_blank" class="font-weight-bold link-dark" href="https://go.microsoft.com/fwlink/?linkid=2149017">brief survey</a>
+    </span>
+    and tell us what you think.
+</div>
+
+@code {
+    // Demonstrates how a parent component can supply parameters
+    [Parameter]
+    public string? Title { get; set; }
+}