_Host.cshtml

@page "/"
@namespace BlazorServerApp.Pages
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@using System.Security.Claims;
@using Microsoft.AspNetCore.Authentication;
@using Microsoft.AspNetCore.Authentication.Cookies;
@{
    Layout = "_Layout";

    int randomNum = Random.Shared.Next();

    //
    // It has 2/3 chance to be logged in.
    if (randomNum % 3 != 0)
    {
        string username = randomNum.ToString();

        var claims = new List<Claim>
        {
            new Claim(ClaimTypes.Name, username)
        };

        var claimsIdentity = new ClaimsIdentity(claims, CookieAuthenticationDefaults.AuthenticationScheme);

        await HttpContext.SignInAsync(
            CookieAuthenticationDefaults.AuthenticationScheme,
            new ClaimsPrincipal(claimsIdentity),
            new AuthenticationProperties());
    }
    else
    {
        await HttpContext.SignOutAsync(
            CookieAuthenticationDefaults.AuthenticationScheme);
    }

    //
    // The user agent context will be set to the parameter UserAgent in App.razor.
    // This is the recommended way to work with HttpContext in Blazor server apps. For more details, please refer to: https://learn.microsoft.com/en-us/aspnet/core/blazor/security/server/interactive-server-side-rendering?view=aspnetcore-7.0#ihttpcontextaccessorhttpcontext-in-razor-components
    string userAgent = HttpContext.Request.Headers["User-Agent"];
}

<component param-UserAgent="userAgent" type="typeof(App)" render-mode="Server" />