具有自身外键的 Net Core ApplicationUser

Question

我正在使用 Net Core 2.2 和实体框架。我有一个 ApplicationUser 类，用于多种用户类型，外键相互连接，但实体框架在添加迁移时出错：

Unable to determine the relationship represented by navigation property 'ApplicationUser.Class' of type 'Class'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'.

我不确定实现此功能的正确方法是什么。谁能帮我？

我的 ApplicationUser 类：

public class ApplicationUser : IdentityUser
{
    public string CustomerId { get; set; }
    public string TeacherId { get; set; }
    public int? ClassId { get; set; }
    public int? SettingsId { get; set; }

    public virtual ApplicationUser Customer { get; set; }
    public virtual ApplicationUser Teacher { get; set; }
    public virtual Class Class { get; set; }
    public virtual Settings Settings { get; set; }
    public virtual ICollection<Class> Classes { get; set; }
    public virtual ICollection<License> Licenses { get; set; }
    public virtual ICollection<Exercise> Exercises { get; set; }
    public virtual ICollection<GameProgress> GameProgresses { get; set; }
    public virtual ICollection<StudentExercise> StudentExercises { get; set; }
}

而且因为它在错误中，我的 Class 类：

public class Class
{
    public int Id { get; set; }
    public string TeacherId { get; set; }
    public int? SettingsId { get; set; }

    public virtual ApplicationUser Teacher { get; set; }
    public virtual Settings Setting { get; set; }
    public virtual ICollection<Exercise> Exercises { get; set; }
    public virtual ICollection<ApplicationUser> Students { get; set; }
}

Answer 1

这个问题与自引用ApplicationUser 关系无关。异常特别告诉您这是Class 的问题。问题是你在ApplicationUser 上有一个对Class 的引用属性，但是在Class 上，你既有ApplicationUsers (Students) 的集合，又有对@987654328 的单独引用@ (Teacher)。简而言之，EF 不知道这个外键实际指的是哪个。

解决方案正是异常告诉您的：添加流利的配置以消除歧义：

public override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<ApplicationUser>()
        .HasOne(x => x.Class)
        .WithMany(x => x.Students);
}