为什么新的身份属性不支持迁移？

Question

我目前正在尝试向Identity添加扩展属性。我看过很多文章，包括：

• Adding properties to IdentityUser doesn't create the correct migration
• https://discussiongenerator.com/2014/04/21/customizing-applicationdbcontext-in-asp-net-mvc-5-and-asp-net-identity-2-0/
• https://blogs.msdn.microsoft.com/webdev/2013/10/16/customizing-profile-information-in-asp-net-identity-in-vs-2013-templates/
• How to extend available properties of User.Identity

这是我目前的模特。

using System.Data.Entity;
using System.Security.Claims;
using System.Threading.Tasks;
using Microsoft.AspNet.Identity;
using Microsoft.AspNet.Identity.EntityFramework;
using System;

namespace website.Models
{
    // You can add profile data for the user by adding more properties to your ApplicationUser class, please visit https://go.microsoft.com/fwlink/?LinkID=317594 to learn more.
    public class ApplicationUser : IdentityUser
    {
        public string ProfilePictureURL { get; set; }
        public DateTime? DateJoined { get; set; }
        public string Description { get; set; }

        public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)
        {
            // Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
            var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);
            // Add custom user claims here
            return userIdentity;
        }

    }

    public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
    {
        public ApplicationDbContext()
            : base("voltageb_websitedatabase", throwIfV1Schema: false)
        {
        }
        public static ApplicationDbContext Create()
        {
            return new ApplicationDbContext();
        }
    }  
}

我遇到的问题是，当我运行“添加迁移”时，它支持空的Up和Down方法。