EntityFrameworkCore-擁有的孩子和另一個連鎖擁有的孩子之間的關系-有解無憂

我被問題困住了，我試圖以正確的方式解決問題。

我有多個一對多的“擁有”關系。但是我在兩個孩子之間有重復的關系 Story 應該有一個 List of Variable s 并且鏈接的孩子Change應該指向這個 List 中的一個變數。我無法將一個類設定為由 2 個物體擁有，并且僅通過“擁有”關系我無法一次保存整個結構。我的代碼結構的示例。

編輯：另一個問題來自TransitionOption，它具有它所屬的 Step 和它指向的下一個Step 。

public class Story //Main structure example class - A before Edit
{
   [Key]
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int Id { get; set; }

   ...name, creator...
   
   [ForeignKey("FK_Story_ID")]
   public List<Step> Steps { get; set; } //Set as OwnsMany

   [ForeignKey("FK_Story_ID")]
   public List<Variable> Variables { get; set; } //Set as OwnsMany , Full list of Variables, that will be shown, which can but does not need to be changed during Step transitions
}

//example class with some main text about changes like part of the story
public class Step 
{
   [Key]
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int Id { get; set; }

   ...some text...

   [ForeignKey("FK_Step_ID")]
   public List<TransitionOption> TransitionOptions { get; set; } //Set as OwnsMany

   public int FK_Story_ID { get; set; }
}

//example class for some option pointing to another Step
public class TransitionOption
{
   [Key]
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int Id { get; set; }       

   [ForeignKey("FK_TransitionOption_ID")]
   public List<Change> Changes { get; set; } //Set as OwnsMany

   public int FK_Step_ID { get; set; }

   public int FK_NextStep_ID { get; set; } //this will also cause problem and I forgot to mention it before Edit
}

//referencing to one Variable from List Variables in Story
public class Change
{
   [Key]
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int Id { get; set; }

   [ForeignKey("FK_Change_ID")]
   public Variable ChangingVariable { get; set; } //Set as OwnsOne/HasOne - or another way around with List of Changes in Variable. But this is more suitable for my case

public int FK_TransitionOption_ID { get; set; }
}

//Child that I need to have in both one Story (Story OwnsMany Variables) and multiple Changes (Change has/owns one Variable respectively Variable has/owns multiple Changes)
public class Variable 
{
   [Key]
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int Id { get; set; }

   ...Starting value, conditions, type (text/number)...

   public int FK_Change_ID { get; set; }
}

狀態將在最終程序中保存，因此我不需要在資料庫中跟蹤它們。這更像是所有轉換和變數的模板和持有者。這個例子展示了一個類似于互動故事的東西。這有點符合我的人際關系。

問題是，我不知道如何最好地為 EF Core 指定這種關系。編輯：另一個問題是TransitionOption具有它所屬的 Step 和它指向的下一個Step 。這個問題我在編輯為更易讀的示例格式時發現了。

我正在嘗試擁有關系 Story-Variable 并擁有擁有關系 Change-Variable 或 Variable-Change ，這會在遷移時引發錯誤。有了Story-Variable 關系，保存會引發外鍵違規，因為 FK 為 0，因為 Story 尚未保存且沒有 ID，而此時 0 以某種方式被視為有效 ID。我想將其全部保存為一個（如果可能）并將其全部加載為一個，因為我有 Angular 前端期望它并將其發送回編輯。

如果缺少某些內容或不容易理解，我會嘗試更好地回答和編輯。感謝所有評論。

我希望有人已經解決了這樣的場景，但是我在檔案中找不到任何類似這樣的案例。請幫忙。

編輯：我已將結構更改為更像我給@grek40 的示例（謝謝）。我不能發布真正的課程，但這個例子應該幾乎是 1:1 的問題，我有。

uj5u.com熱心網友回復：

基本上，OwnsMany這是一種特殊的關系，當您有多個具有導航屬性的物體到同一個目標時，這種關系就不適合了。在這種情況下，您應該使用HasMany關系。

當您對同一個物體有多個參考（例如TransitionOptions屬于 someCurrentStep并指向 some NextStep）時，請使用 FluentApi 或用注釋InversePropertyAnnotation，而不是用ForeignKeyAnnotation。

一般來說，我建議你使用更流暢的 api 配置和更少的基于注釋的配置——它更容易維護。

這是基于您的問題的一些示例代碼。

模型類

public class Story
{
    public int Id { get; set; }

    public List<Step>? Steps { get; set; }

    public List<Variable>? Variables { get; set; }
}

public class Variable
{
    public int Id { get; set; }

    public int StoryId { get; set; }

    public string? Value { get; set; }

    public Story? Story { get; set; }

    public List<Change>? Changes { get; set; }
}

public class Step
{
    public int Id { get; set; }

    public int StoryId { get; set; }

    public Story? Story { get; set; }

    public List<TransitionOption>? TransitionOptions { get; set; }
}

public class TransitionOption
{
    public int Id { get; set; }

    public int StepId { get; set; }

    public int? NextStepId { get; set; }

    public Step? CurrentStep { get; set; }

    public Step? NextStep { get; set; }
    
    public List<Change>? Changes { get; set; }
}

public class Change
{
    // If combination of TransitionOptionId and VariableId is unique,
    // you can use them as composite key instead
    public int Id { get; set; }

    public int TransitionOptionId { get; set; }

    public int VariableId { get; set; }

    public Variable? Variable { get; set; }

    public TransitionOption? TransitionOption { get; set; }
}

物體配置類

internal class StoryConfiguration : IEntityTypeConfiguration<Story>
{
    public void Configure(EntityTypeBuilder<Story> builder)
    {
        builder.HasMany(x => x.Variables)
            .WithOne(x => x.Story)
            .HasForeignKey(x => x.StoryId)
            .OnDelete(DeleteBehavior.Cascade);

        builder.HasMany(x => x.Steps)
            .WithOne(x => x.Story)
            .HasForeignKey(x => x.StoryId)
            .OnDelete(DeleteBehavior.Cascade);
    }
}
internal class VariableConfiguration : IEntityTypeConfiguration<Variable>
{
    public void Configure(EntityTypeBuilder<Variable> builder)
    {
        builder.HasMany(x => x.Changes)
            .WithOne(x => x.Variable)
            .HasForeignKey(x => x.VariableId)
            .OnDelete(DeleteBehavior.Cascade);
    }
}
internal class StepConfiguration : IEntityTypeConfiguration<Step>
{
    public void Configure(EntityTypeBuilder<Step> builder)
    {
        builder.HasMany(x => x.TransitionOptions)
            .WithOne(x => x.CurrentStep)
            .HasForeignKey(x => x.StepId)
            .OnDelete(DeleteBehavior.Cascade);

        // No navigation property in Step for TransitionOptions pointing
        // to this as NextStep.
        // It would also be possible to define such a property and mention it
        // in HasMany
        builder.HasMany<TransitionOption>()
            .WithOne(x => x.NextStep)
            .HasForeignKey(x => x.NextStepId)
            // If next step is deleted, only disconnect referencing TransitionOptions
            .OnDelete(DeleteBehavior.SetNull);
    }
}
internal class TransitionOptionConfiguration : IEntityTypeConfiguration<TransitionOption>
{
    public void Configure(EntityTypeBuilder<TransitionOption> builder)
    {
        builder.HasMany(x => x.Changes)
            .WithOne(x => x.TransitionOption)
            .HasForeignKey(x => x.TransitionOptionId)
            .OnDelete(DeleteBehavior.Cascade);
    }
}

在方法中應用配置OnModelCreating。

使用 1 創建整個故事結構的示例方法SaveChanges

public async Task InitDb(MyDatabase db)
{
    var variable1 = new Variable
    {
        Value = "1st Value"
    };
    db.Stories?.Add(new Story
    {
        Variables = new List<Variable>
        {
            variable1
        },
        Steps = new List<Step>
        {
            new Step
            {
                TransitionOptions = new List<TransitionOption>
                {
                    new TransitionOption
                    {
                        Changes = new List<Change>
                        {
                            new Change
                            {
                                Variable=variable1
                            }
                        }
                    }
                }
            }
        }
    });
    await db.SaveChangesAsync();
}

希望此示例顯示您所描述的結構所需的一切。

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