在.NET Core 2.1中，使用ASP.NET Identity进行身份验证的解决方法如下：

1. 创建一个新的ASP.NET Core 2.1项目。
2. 在项目文件中添加以下依赖关系：

3. 创建一个新的IdentityContext类，继承自IdentityDbContext：

using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;

namespace YourNamespace
{
    public class IdentityContext : IdentityDbContext
    {
        public IdentityContext(DbContextOptions options) : base(options)
        {
        }
    }
}

4. 在Startup.cs文件中进行配置：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Identity;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using YourNamespace;

public class Startup
{
    private readonly IConfiguration _configuration;

    public Startup(IConfiguration configuration)
    {
        _configuration = configuration;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext(options =>
            options.UseSqlServer(_configuration.GetConnectionString("DefaultConnection")));

        services.AddIdentity()
            .AddEntityFrameworkStores()
            .AddDefaultTokenProviders();

        services.Configure(options =>
        {
            options.Password.RequireDigit = true;
            options.Password.RequireLowercase = true;
            options.Password.RequireNonAlphanumeric = true;
            options.Password.RequireUppercase = true;
            options.Password.RequiredLength = 6;
            options.Password.RequiredUniqueChars = 1;
        });

        services.ConfigureApplicationCookie(options =>
        {
            options.Cookie.HttpOnly = true;
            options.ExpireTimeSpan = TimeSpan.FromMinutes(30);
            options.LoginPath = "/Account/Login";
            options.LogoutPath = "/Account/Logout";
            options.AccessDeniedPath = "/Account/AccessDenied";
            options.SlidingExpiration = true;
        });

        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
            app.UseDatabaseErrorPage();
        }
        else
        {
            app.UseExceptionHandler("/Home/Error");
            app.UseHsts();
        }

        app.UseHttpsRedirection();
        app.UseStaticFiles();
        app.UseAuthentication(); // 添加身份验证中间件

        app.UseMvc(routes =>
        {
            routes.MapRoute(
                name: "default",
                template: "{controller=Home}/{action=Index}/{id?}");
        });
    }
}

5. 创建一个AccountController，用于处理用户登录和注册：

using System.Threading.Tasks;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;
using YourNamespace.Models;

public class AccountController : Controller
{
    private readonly UserManager _userManager;
    private readonly SignInManager _signInManager;

    public AccountController(
        UserManager userManager,
        SignInManager signInManager)
    {
        _userManager = userManager;
        _signInManager = signInManager;
    }

    [HttpGet]
    public IActionResult Register()
    {
        return View();
    }

    [HttpPost]
    public async Task Register(RegisterViewModel model)
    {
        if (ModelState.IsValid)
        {
            var user = new IdentityUser { UserName = model.Email, Email = model.Email };
            var result = await _userManager.CreateAsync(user, model.Password);
            if (result.Succeeded)
            {
                await _signInManager.SignInAsync(user, isPersistent: false);
                return RedirectToAction("Index", "Home");
            }
            foreach (var error in result.Errors)
            {
                ModelState.AddModelError("", error.Description);
            }
        }
        return View(model);
    }

    [HttpGet]
    public IActionResult Login()
    {
        return View();
    }

    [HttpPost]
    public async Task Login(LoginViewModel model, string returnUrl = null)
    {
        returnUrl = returnUrl ?? Url.Content("~/");
        if (ModelState.IsValid)
        {
            var result = await _signInManager.PasswordSignInAsync(model.Email, model.Password, model.RememberMe, lockoutOnFailure: false);
            if (result.Succeeded)
            {
                return LocalRedirect(returnUrl);
            }
            ModelState.AddModelError(string.Empty, "Invalid login attempt.");
        }
        return View(model);
    }

    [HttpPost]
    public async Task Logout()
    {
        await _signInManager