我正试着把数据输入我的数据库。我有Photos和AppUser两节课。它们具有ICollection<Photo> Photos属性的一对多关系，这意味着每个用户可以拥有多个图像。
AppUser类：

public class AppUser
 {
 public int Id { get; set; }
 public string UserName { get; set; }
 public byte[] PasswordHash { get; set; }
 public byte[] PasswordSalt { get; set; }
 public DateTime DateOfBirth { get; set; }
 public string KnownAs { get; set; }
 public DateTime Created { get; set; } = DateTime.Now;
 public DateTime LastSeen { get; set; } = DateTime.Now;
 public string Gender { get; set; }
 public string Introduction { get; set; }
 public string LookingFor { get; set; }
 public string Interests { get; set; }
 public string City { get; set; }
 public string Country { get; set; }
 public ICollection<Photo> Photos { get; set; }
}

Photo类：

namespace API.Entity
{
[Table("Photos")]
public class Photo
{
 public int Id { get; set; }
 public string UrL { get; set; }
 public bool IsMain { get; set; }
 public string PublicId { get; set; }
 public AppUser AppUser { get; set; }
 public int AppUserId { get; set; }
}
}

Seed类：

public class Seed
 {
 public static async Task SeedUsers(DataContext context)
 {
 if (await context.Users.AnyAsync()) return;
 var userData = await System.IO.File.ReadAllTextAsync("Data/UserSeedData.json");
 var users = JsonSerializer.Deserialize<List<AppUser>>(userData);
 if (users == null) return;
 foreach (var user in users)
 {
   using var hmac = new HMACSHA512();
   user.UserName = user.UserName.ToLower();
   user.PasswordSalt = hmac.Key;
   user.PasswordHash = hmac.ComputeHash(Encoding.UTF8.GetBytes("pa$$w0rd"));

  await context.Users.AddAsync(user);
  }
  await context.SaveChangesAsync();
  }
 }

生成种子数据的JSON文件(我有很多，这是其中之一)：

[
 {
 "UserName": "Sandy",
 "Gender": "female",
 "DateOfBirth": "1978-02-23",
 "KnownAs": "Sandy",
 "Created": "2019-07-28",
 "LastActive": "2020-05-24",
 "Introduction": "Cupidatat do nostrud et culpa commodo enim minim quis. 
 "Interests": "Esse sunt sit fugiat tempor voluptate cillum mollit aliquip irure ipsum mollit quis",
 "City": "Moscow",
 "Country": "Denmark",

   "Photos": [
      {

      "Url": "https://randomuser.me/api/portraits/women/42.jpg",
      "IsMain": true
     }

    ]
    }
    ]

Photo表中的URL设置为空。尽管设置了“IsMain”属性，但设置了它的值并且运行良好。我尝试删除迁移并重新开始，但仍然为空。我想不通了。