EF多對多導致重複

我有多對多關係的問題，因爲它會導致重複記錄。EF多對多導致重複

我有這些類：

class Flyer { Id, virtual ICollection<FlyerPage> Pages } 

class FlyerPage { Id, FlyerId, virtual Flyer Flyer, ICollection<FlyerPageKeyword> Keywords }

而且

class FlyerPageKeyword { Id, Key, virtual ICollection<FlyerPage> Pages }

所以FlyerPage和FlyerPageKeyword是多對多。它的工作原理和記錄保存到數據庫。

但它也增加了關鍵字的重複。

我的背景：

public class Context : DbContext 
{ 
    public Context() : base("name=DbConnectionString") 
    { 
     Database.SetInitializer(new CreateDatabaseIfNotExists<Context>()); 
    } 

    public virtual DbSet<Flyer> Flyers { get; set; } 

    protected override void OnModelCreating(DbModelBuilder modelBuilder) 
    { 
     base.OnModelCreating(modelBuilder); 
     modelBuilder.Conventions.Remove<PluralizingTableNameConvention>(); 

     modelBuilder.Configurations.Add(new FlyersEntityConfiguration()); 
     modelBuilder.Configurations.Add(new FlyersPageEntityConfiguration()); 
     modelBuilder.Configurations.Add(new FlyersPageKeywordsEntityConfiguration()); 
    } 
} 



public class FlyersEntityConfiguration : EntityTypeConfiguration<Flyer> 
{ 
    public FlyersEntityConfiguration() 
    { 
     this.Map(flyer => flyer.ToTable("Flyer", "Flyers")); 

     this.HasMany(flyer => flyer.Pages) 
      .WithRequired(page => page.Flyer) 
      .HasForeignKey(page => page.FlyerId); 
    } 
} 

public class FlyersPageEntityConfiguration : EntityTypeConfiguration<FlyerPage> 
{ 
    public FlyersPageEntityConfiguration() 
    { 
     this.Map(pages => pages.ToTable("Page", "Flyers")); 
     this.HasMany(page => page.Keywords).WithMany(keywords => keywords.FlyerPages).Map(cfg => 
     { 
      cfg.ToTable("PageKeywords", "Flyers.Page"); 
      cfg.MapLeftKey("FlyerPageId"); 
      cfg.MapRightKey("KeywordId"); 
     }); 
    } 
} 
public class FlyersPageKeywordsEntityConfiguration : EntityTypeConfiguration<FlyerPageKeyword> 
{ 
    public FlyersPageKeywordsEntityConfiguration() 
    { 
     this.ToTable("Keyword", "Flyers.Page"); 
    } 
}

而且Flyer是聚合根，所以我就可以進行操作。無法只保存關鍵字。

var context = new Context(); 
     var flyer = new Flyer 
     { 
      Pages = new List<FlyerPage> 
      { 
       new FlyerPage 
       { 
        Id = Guid.NewGuid(), 
        Keywords = new List<FlyerPageKeyword> {new FlyerPageKeyword {Key = "One"}} 
       }, 
       new FlyerPage 
       { 
        Keywords = new List<FlyerPageKeyword> {new FlyerPageKeyword {Key = "Two"}} 
       } 
      } 
     }; 
     context.Flyers.Add(flyer); 
     context.SaveChanges();

來源

2017-04-25 Nerf

是'FlyerPage'和'FlyerPages'相同的（錯誤）？ – grek40

是的，這是拼寫錯誤。 – Nerf

你能澄清這個問題嗎？ 'FlyerPageId，KeywordId'的組合應該與您當前的設計是唯一的。 –

避免重複，傳單分配應該像

var context = new Context(); 
     var flyer = new Flyer 
     { 
      Pages = new List<FlyerPage> 
      { 
       new FlyerPage 
       { 
        Id = Guid.NewGuid(), 
        Keywords = new List<FlyerPageKeyword> 
         { 
          context.Keywords.FirstOrDefault(x => x.Key == "One") ?? new FlyerPageKeyword {Key = "One"} 
         } 


       }, 
       new FlyerPage 
       { 
        Keywords = new List<FlyerPageKeyword> 
         { 
          context.Keywords.FirstOrDefault(x => x.Key == "Two")?? new FlyerPageKeyword {Key = "Two"} 
         } 
       } 
      } 
     }; 
     context.Flyers.Add(flyer); 
     context.SaveChanges();

來源

2017-04-25 11:47:33

基本上它的所有關於使用現有的關鍵字條目，創建新對象之前：

someKeyword = context.Keywords.FirstOrDefault(x => x.Key == "One") ?? new FlyerPageKeyword {Key = "One"};

如果你只是new它已經存在的關鍵字，你會得到你的副本。

來源

2017-04-25 11:20:07 grek40

EF多對多導致重複

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