1. 在Startup.cs文件中，添加以下代码以启用cookie：

public void ConfigureServices(IServiceCollection services)
{
    // ...
    services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
        .AddCookie(options =>
        {
            options.Cookie.Name = "cookieName";
            options.Cookie.SameSite = SameSiteMode.Strict;
            options.Cookie.SecurePolicy = CookieSecurePolicy.Always;
            options.Cookie.HttpOnly = true;
            options.Cookie.IsEssential = true;
            options.LoginPath = "/Account/Login";
            options.LogoutPath = "/Account/Logout";
            options.AccessDeniedPath = "/Account/AccessDenied";
        });
    // ...
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // ...
    app.UseRouting();
    app.UseAuthentication();
    app.UseAuthorization();
    // ...
}

2. 在Controller中使用以下代码来获取cookieValue：

[HttpGet]
public IActionResult Index()
{
    string cookieValue = HttpContext.Request.Cookies["cookieName"];
    if (string.IsNullOrEmpty(cookieValue))
    {
        cookieValue = Guid.NewGuid().ToString();
        var cookieOptions = new CookieOptions
        {
            HttpOnly = true,
            Secure = true,
            SameSite = SameSiteMode.Strict,
            Expires = DateTimeOffset.UtcNow.AddDays(7)
        };
        HttpContext.Response.Cookies.Append("cookieName", cookieValue, cookieOptions);
    }
    return View();
}

通过添加上述代码，我们就可以在ASP.NET Core应用程序的第一个请求/响应中获取cookieValue了。