下面是一个示例解决方案，演示了如何在ASP.NET Core MVC中实现两因素电子邮件确认（无身份验证）。

1. 创建一个ASP.NET Core MVC项目。
2. 安装必需的NuGet包：
   • Microsoft.AspNetCore.Authentication
   • Microsoft.AspNetCore.Identity
   • Microsoft.EntityFrameworkCore
   • Microsoft.EntityFrameworkCore.SqlServer
   • Microsoft.Extensions.DependencyInjection
   • Microsoft.Extensions.Logging
   • Microsoft.VisualStudio.Web.CodeGeneration.Design
3. 创建一个EmailConfirmation模型来存储电子邮件确认信息：

   public class EmailConfirmation
   {
       public int Id { get; set; }
       public string UserId { get; set; }
       public string Token { get; set; }
       public DateTime CreatedAt { get; set; }
   }
   

4. 在IdentityUser类的派生类中添加一个EmailConfirmed属性，用于跟踪用户是否已确认电子邮件：

   public class ApplicationUser : IdentityUser
   {
       public bool EmailConfirmed { get; set; }
   }
   

5. 创建一个EmailConfirmationDbContext类，用于处理电子邮件确认的数据库操作：

   public class EmailConfirmationDbContext : DbContext
   {
       public DbSet EmailConfirmations { get; set; }
   
       public EmailConfirmationDbContext(DbContextOptions options) : base(options)
       {
       }
   }
   

6. 在Startup.cs文件的ConfigureServices方法中配置Identity服务和电子邮件确认数据库上下文：

   public void ConfigureServices(IServiceCollection services)
   {
       // ...
   
       services.AddDbContext(options =>
           options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
   
       services.AddIdentity()
           .AddEntityFrameworkStores()
           .AddDefaultTokenProviders();
   
       // ...
   }
   

7. 创建一个电子邮件服务类，用于发送验证链接给用户：

   public class EmailService
   {
       private readonly IEmailSender _emailSender;
   
       public EmailService(IEmailSender emailSender)
       {
           _emailSender = emailSender;
       }
   
       public async Task SendConfirmationEmail(ApplicationUser user, string confirmationLink)
       {
           await _emailSender.SendEmailAsync(user.Email, "Confirm your email",
               $"Please confirm your email by clicking this link: link");
       }
   }
   

8. 在AccountController中添加一个SendConfirmationEmail方法，用于生成电子邮件确认链接并发送给用户：

   private readonly EmailConfirmationDbContext _emailConfirmationDbContext;
   private readonly EmailService _emailService;
   
   public AccountController(EmailConfirmationDbContext emailConfirmationDbContext, EmailService emailService)
   {
       _emailConfirmationDbContext = emailConfirmationDbContext;
       _emailService = emailService;
   }
   
   [HttpGet]
   [AllowAnonymous]
   public async Task SendConfirmationEmail(string userId)
   {
       var user = await _userManager.FindByIdAsync(userId);
       if (user == null)
       {
           return NotFound();
       }
   
       var token = Guid.NewGuid().ToString();
   
       var emailConfirmation = new EmailConfirmation
       {
           UserId = user.Id,
           Token = token,
           CreatedAt = DateTime.UtcNow
       };
   
       _emailConfirmationDbContext.EmailConfirmations.Add(emailConfirmation);
       await _emailConfirmationDbContext.SaveChangesAsync();
   
       var confirmationLink = Url.Action("ConfirmEmail", "Account",
           new { userId = user.Id, token = token }, Request.Scheme);
   
       await _emailService.SendConfirmationEmail(user, confirmationLink);
   
       return Ok();
   }
   

9. 创建一个ConfirmEmail方法，用于处理用户点击电子邮件确认链接的请求：

   [HttpGet]
   [AllowAnonymous]
   public async Task ConfirmEmail(string userId, string token)
   {
       var user = await _userManager.FindByIdAsync(userId);
       if (user == null)
       {
           return NotFound();
       }
   
       var emailConfirmation = await _emailConfirmationDbContext.EmailConfirmations
           .SingleOrDefaultAsync(ec => ec.UserId == userId && ec.Token == token);
   
       if (emailConfirmation == null)
       {
           return BadRequest();
       }
   
       emailConfirmation.EmailConfirmed = true;
       _emailConfirmationDbContext.EmailConfirmations.Remove(emailConfirmation);
       await _emailConfirmationDbContext.SaveChangesAsync();
   
       return Ok();
   }
   

10. 在注册用户时，将EmailConfirmed属性设置为false，并