DEMOMySql/WebApp/Blazor/Blazor.App.Web/App.razor

<CascadingAuthenticationState>
  <Router AppAssembly="@typeof(Program).Assembly" AdditionalAssemblies="new[] { typeof(MainLayout).Assembly }">
    <Found Context="routeData">
             <AuthorizeRouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)">
                <NotAuthorized>
                    @if (!context.User.Identity.IsAuthenticated)
                    {
                        <RedirectToLogin />
                    }
                    else
                    {
                        <p>You are not authorized to access this resource.</p>
                    }
                </NotAuthorized>
            </AuthorizeRouteView>
    </Found>
    <NotFound>
        <LayoutView Layout="@typeof(MainLayout)">
            <p>Sorry, there's nothing at this address.</p>
        </LayoutView>
    </NotFound>
  </Router>
</CascadingAuthenticationState>