c# – EF7(Core)中同一个表的多个关系

我有这样的模特

public class Question
{
    public string Id { get; set; } = Guid.NewGuid().ToString();
 
    public Answer Answer { get; set; }
    public List<Variant> Variants { get; set; }
 
    public string CorrectVariantId { get; set; }
    public Variant CorrectVariant { get; set; }
}
 
public class Variant
{
    public string Id { get; set; } = Guid.NewGuid().ToString();
 
    public string QuestionId { get; set; }
    public Question Question { get; set; }
}
 
// mapping
 
modelBuilder.Entity<Question>()
    .HasOne(q => q.CorrectVariant)
    .WithOne(v => v.Question)
    .HasForeignKey<Question>(q => q.CorrectVariantId);
 
modelBuilder.Entity<Variant>()
    .HasOne(v => v.Question)
    .WithMany(a => a.Variants)
    .OnDelete(DeleteBehavior.Cascade);

在从EF RC1升级到RTM之前,这种方法非常有效.但现在它抛出：
System.InvalidOperationException：无法在’Question.Variants’和’Variant.Question’之间创建关系,因为’Question.CorrectVariant’和’Variant.Question’之间已经存在关系.导航属性只能参与单个关系.

如果没有从Question模型中删除Variants属性,是否有解决此问题的方法？

@H_502_10@解决方法

这是RC1中的一个错误/不受欢迎的行为,它已得到修复.

你应该创建另一个属性,比如说另一个关系的SecondQuestion.

public class Question
{
  public string Id { get; set; } = Guid.NewGuid().ToString();
  public List<Variant> Variants { get; set; }
 
  public string CorrectVariantId { get; set; }
  public Variant CorrectVariant { get; set; }
}
 
public class Variant
{
  public string Id { get; set; } = Guid.NewGuid().ToString();
 
  public string QuestionId { get; set; }
  public Question Question { get; set; }
 
  public Question SecondQuestion { get; set; }
}

你的DbContext：

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
  modelBuilder.Entity<Question>()
    .HasOne(q => q.CorrectVariant)
    .WithOne(v => v.SecondQuestion)
    .HasForeignKey<Question>(q => q.CorrectVariantId);
 
  modelBuilder.Entity<Variant>()
      .HasOne(v => v.Question)
      .WithMany(a => a.Variants).HasForeignKey(x => x.QuestionId).OnDelete(DeleteBehavior.SetNull);
 
  base.OnModelCreating(modelBuilder);
}

如何使用它：

using (var myDb = new MyDbContext())
{
  var variantFirst = new Variant();
  var variantSecond = new Variant();
 
  var question = new Question();
  variantFirst.Question = question;
 
  variantSecond.SecondQuestion = question;
 
  myDb.Variants.Add(variantFirst);
  myDb.Variants.Add(variantSecond);
 
  myDb.SaveChanges();
}

c# – EF7(Core)中同一个表的多个关系

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