EF 外鍵約束

Question

我仍在研究實體框架並嘗試創建一個包含外鍵的 model。

但是當我嘗試遷移代碼時，出現了這個錯誤

在表“QuestionResults”上引入 FOREIGN KEY 約束“FK_dbo.QuestionResults_dbo.QuestionsTables_QuetionsTableId”可能會導致循環或多個級聯路徑。 指定ON DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他FOREIGN KEY約束

這些是我的 model 課程：

public class MainDetails
{
    [Key]
    public int Id { get; set; }
    public string Language { get; set; }

    [Required]
    public string CustomerName { get; set; }

    [Required]
    public string ContactNumber { get; set; }
    public string EmailAddress { get; set; }

    [DisplayName("Service Type")]
    [ForeignKey("QuestionsTable")]
    public int ServiceTypeId { get; set; }
    public virtual QuestionsTable QuestionsTable { get; set; }

    [Required]
    public string VehicleNumber { get; set; }

    [Required]
    public string ServiceLocation { get; set; }
    public string Suggestion { get; set; }
    public bool Status { get; set; } = true;

    [DataType(DataType.Date)]
    [DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}", ApplyFormatInEditMode = true)]
    [Display(Name = "Created Date")]
    public DateTime CreatedDate { get; set; } = DateTime.Now;

    public virtual QuestionResults QuestionResults { get; set; }

    public virtual IList<QuestionResults> QuestionResultsMainlist { get; set; }
    public virtual IList<QuestionsTable> QuestionsTables { get; set; }
}

public class QuestionsTable
{
    [Key]
    public int Id { get; set; }
    public string ServiceType { get; set; }
    public string Question { get; set; }
    public virtual IList<MainDetails> MainDetailsServiceType { get; set; }
    public QuestionsTable()
    {
        MainDetailsServiceType = new List<MainDetails>();
    }
}

public class QuestionResults
{
    [Key]
    public int Id { get; set; }

    [DisplayName("MainDetail ID")]
    [ForeignKey("MainDetails")]
    public int MainDetailsId { get; set; }
    public virtual MainDetails MainDetails { get; set; }

    [DisplayName("MainDetail ID")]
    [ForeignKey("QuestionsTable")]
    public int QuetionsTableId { get; set; }
    public virtual QuestionsTable QuestionsTable { get; set; }

    [Required]
    public string CustoAnswer { get; set; }
}

這是我要創建的表結構：

Answer 1

要解決此問題，您可以使用 EF Model Builder

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{   
    modelBuilder.Entity<QuestionsTable>()
        .HasRequired(a => a.MainDetails)
        .WithOptionalDependent()
        .WillCascadeOnDelete(false); //This is the important row
}

您必須考慮您想要的關系類型以及是否明確指定外鍵。 如果您之前沒有見過這個 model 構建器，請閱讀此處： https://learn.microsoft.com/en-us/ef/core/modeling/

---

在分解您的場景后，我注意到了一些“奇怪之處”。 我將域 model 中的噪聲從您的示例降低到這個

public class MainDetails
{
    [Key]
    public int Id { get; set; }

    [ForeignKey("QuestionsTable")]
    public int ServiceTypeId { get; set; }
    
    public virtual QuestionsTable QuestionsTable { get; set; }

    public virtual QuestionResults QuestionResults { get; set; }

    public virtual IList<QuestionResults> QuestionResultsMainlist { get; set; }
    
    public virtual IList<QuestionsTable> QuestionsTables { get; set; }
}

public class QuestionsTable
{
    [Key]
    public int Id { get; set; }
    public string ServiceType { get; set; }
    public string Question { get; set; }
    public virtual IList<MainDetails> MainDetailsServiceType { get; set; }
}

public class QuestionResults
{
    [Key]
    public int Id { get; set; }

    [ForeignKey("MainDetails")]
    public int MainDetailsId { get; set; }
    public virtual MainDetails MainDetails { get; set; }

    [ForeignKey("QuestionsTable")]
    public int QuetionsTableId { get; set; }
    public virtual QuestionsTable QuestionsTable { get; set; }
}

我注意到了一些事情。

• MainDetails 包含一對多（QuestionTable）和多對多（IList）關系？ 我不確定你的意圖
• QuestionsResults 包含與未在 QuestionTable class 中復制的兩個實體的單一關系？ 如果是故意的就好了
• ServiceType 是 QuestionsTable 中的字符串，但您期望 int 作為 MainDetails 中的外鍵？