Question

我正在使用.NET CORE 2.1构建平台，它是关于问题和答案的平台。在开始之前，我将现有的数据库脚手架放入.net项目中，因此我启动了模型并开始运行。

Scaffold-DbContext“服务器=（localdb）\ mssqllocaldb;数据库= MYDATABASE; Trusted_Connection = True;” Microsoft.EntityFrameworkCore.SqlServer -OutputDir模型

但是它生成了具有多对一关系的QUESTION和QUESTION_DETAIL，而QUESTION应该只有1个QUESTION DETAIl。但是，当我尝试在上下文中使用流畅的API进行更改时，会出现错误：

无法将lambda表达式转换为类型“类型”，因为它不是委托类型

这是我的2个模型课程

public partial class Question
{
    public Question()
    {
        AnswerClientBot = new HashSet<AnswerClientBot>();
        InverseOriginalQuestion = new HashSet<Question>();
        QuestionFollowUpFollowUpQuestion = new HashSet<QuestionFollowUp>();
        QuestionFollowUpOriginalQuestion = new HashSet<QuestionFollowUp>();
    }

    public int Id { get; set; }
    public int BotInstanceId { get; set; }
    public string LanguageCode { get; set; }
    public string Question1 { get; set; }
    public int? OriginalQuestionId { get; set; }
    [ForeignKey("QuestionDetail")]
    public int QuestionDetailId { get; set; }

    public Instance BotInstance { get; set; }
    public Question OriginalQuestion { get; set; }
    public QuestionDetail QuestionDetail { get; set; }
    public ICollection<AnswerClientBot> AnswerClientBot { get; set; }
    public ICollection<Question> InverseOriginalQuestion { get; set; }
    public ICollection<QuestionFollowUp> QuestionFollowUpFollowUpQuestion { get; set; }
    public ICollection<QuestionFollowUp> QuestionFollowUpOriginalQuestion { get; set; }
}

public partial class QuestionDetail
{
    public int Id { get; set; }
    public int OriginalQuestionId { get; set; }
    public string Topic { get; set; }
    public string Intent { get; set; }
    public string CustDetail01 { get; set; }
    public string CustDetail02 { get; set; }
    public string CustDetail03 { get; set; }
    public string CustDetail04 { get; set; }
    public string CustDetail05 { get; set; }
    public string Keywords { get; set; }

    public Question OriginalQuestion { get; set; }
}

这是我要更改的上下文，错误发生在

HasForeignKey(d => d.OriginalQuestionId)

modelBuilder.Entity<QuestionDetail>(entity =>
        {
            entity.ToTable("QuestionDetail", "Bot");

            entity.Property(e => e.CustDetail01)
                .HasColumnName("CUST_Detail01")
                .HasMaxLength(250)
                .IsUnicode(false);

            entity.Property(e => e.CustDetail02)
                .HasColumnName("CUST_Detail02")
                .HasMaxLength(250)
                .IsUnicode(false);

            entity.Property(e => e.CustDetail03)
                .HasColumnName("CUST_Detail03")
                .HasMaxLength(250)
                .IsUnicode(false);

            entity.Property(e => e.CustDetail04)
                .HasColumnName("CUST_Detail04")
                .HasMaxLength(250)
                .IsUnicode(false);

            entity.Property(e => e.CustDetail05)
                .HasColumnName("CUST_Detail05")
                .HasMaxLength(250)
                .IsUnicode(false);

            entity.Property(e => e.Intent)
                .HasMaxLength(250)
                .IsUnicode(false);

            entity.Property(e => e.Keywords)
                .HasMaxLength(250)
                .IsUnicode(false);

            entity.Property(e => e.Topic)
                .HasMaxLength(250)
                .IsUnicode(false);

            entity.HasOne(d => d.OriginalQuestion)
                .WithOne(p => p.QuestionDetail)
                .HasForeignKey(d => d.OriginalQuestionId)
                .OnDelete(DeleteBehavior.ClientSetNull)
                .HasConstraintName("FK_Bot_QuestionDetail_OriginalQuestionId");
        });

有人知道我该如何解决吗？谢谢！

Answer 1

相互声明两个具有导航属性的类。在其主键上用ForeignKey属性标记一个表（从属表）。 EF从中推断出一对一：

public class Question
{
    ...
    //  [ForeignKey("QuestionDetail")]
    //  public int QuestionDetailId { get; set; }
    public QuestionDetail QuestionDetail { get; set; }
    ...
}
public partial class QuestionDetail
{
   //public int Id { get; set; }
   [ForeignKey("Question")]
   public int QuestionId { get; set; }
   ...
   public Question Question { get; set; }
}

Answer 2

因此，我找到了这个Cannot convert lambda expression to type 'object' because it is not a delegate type stackoverflow帖子，一开始我试图对其进行强类型化，但实际上却不知道该怎么做，但最终我发现了。因此，我将其更改为HasForeignKey<Question>(d => d.OriginalQuestionId)对我有用。

将多对一关系转换为一对一EF

2 个答案: