Applying Layouts in ASP.NET Core Blazor

Apply a layout to a component

@page "/episodes"
@layout DoctorWhoLayout

<h2>Episodes</h2>

<ul>
    <li>
        <a href="https://www.bbc.co.uk/programmes/p00vfknq">
            <em>The Ribos Operation</em>
        </a>
    </li>
    <li>
        <a href="https://www.bbc.co.uk/programmes/p00vfdsb">
            <em>The Sun Makers</em>
        </a>
    </li>
    <li>
        <a href="https://www.bbc.co.uk/programmes/p00vhc26">
            <em>Nightmare of Eden</em>
        </a>
    </li>
</ul>

Apply a layout to a folder of components

_Imports.razor:

@layout DoctorWhoLayout
...

Apply a default layout to an app

App.razor:

<Router AppAssembly="@typeof(Program).Assembly">
    <Found Context="routeData">
        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
    </Found>
    <NotFound>
        <p>Sorry, there's nothing at this address.</p>
    </NotFound>
</Router>

Apply a layout to arbitrary content (LayoutView component)

App.razor:

<Router AppAssembly="@typeof(Program).Assembly">
    <Found Context="routeData">
        <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
    </Found>
    <NotFound>
        <LayoutView Layout="@typeof(ErrorLayout)">
            <h1>Page not found</h1>
            <p>Sorry, there's nothing at this address.</p>
        </LayoutView>
    </NotFound>
</Router>

References
https://docs.microsoft.com/en-us/aspnet/core/blazor/components/layouts?view=aspnetcore-6.0#apply-a-layout