Entity Framework Code First: Entity Association and DB Migration

前言

最近在研讀 ASP.NET MVC 5 : 網站開發美學 4.6.3 / 4.6.4 / 4.8 時, 將書中範例作了一次演練整合, 包含以下內容;

• 定義或變更欄位的資料庫型態
• 加入欄位
• 1 to 1 關聯
• 1 to many 關聯
• many to many 關聯
• 資料庫移轉 (Database Migration)

在閱讀本文的同時, 可以參考 ASP.NET MVC 5 : 網站開發美學 書中的章節作對照.

過程

• 1. 建立 Console 專案

• 2. 加入 ADO.NET 實體資料模型 --> 空的 Code First 模型 (BlogModel)

• 3. 進行 Initial 資料庫的建立

• • 加入 Blog.cs / BlogArticle.cs ( 1 : n )
  • • public class Blog
    • {
    •     public int Id { get; set; }
    •     public Guid OwnerId { get; set; }
    •     public string Caption { get; set; }
    •     public DateTime DateCreated { get; set; }
    • }
    •  
    • public class BlogArticle
    • {
    •     public Guid Id { get; set; }
    •     public int BlogId { get; set; }
    •     public string Subject { get; set; }
    •     public string Body { get; set; }
    •     public DateTime DateCreated { get; set; }
    •     public DateTime DateModified { get; set; }
    • }
    • 
      
  • 修改 BlogModel.cs
  • • public virtual DbSet<Blog> Blogs { get; set; }
    • public virtual DbSet<BlogArticle> BlogArticles { get; set; }
    •  
    • protected override void OnModelCreating(DbModelBuilder modelBuilder)
    • {
    •     var blogTable = modelBuilder.Entity<Blog>().ToTable("Blogs");
    •     var blogArticleTable = modelBuilder.Entity<BlogArticle>().ToTable("BlogArticles");
    •     blogTable.Property(c => c.Id).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.BlogId).IsRequired().HasColumnType("bigint");
    •   base.OnModelCreating(modelBuilder);
    • }
  • 加入 MyDbInitializer 類別 (in Program.cs)
  • • class MyDbInitializer : IDatabaseInitializer<BlogModel>
    • {
    •     public void InitializeDatabase(BlogModel context)
    •     {
    •         //context.Database.Delete();
    •         context.Database.CreateIfNotExists();
    •     }
    • }
  • 修改 Program.cs
  • • static void Main(string[] args)
    • {
    •     using (BlogModel context = new BlogModel() )
    •     {
    •         // 方式一:
    •         // context.Database.CreateIfNotExists();     //如果資料庫不存在, 就建立
    •         // 方式二: 透過 IDatabaseInitializer<T> 的實作
    •         Database.SetInitializer(new MyDbInitializer()); // set initializer
    •         context.Database.Initialize(true);  // run initializer, 這裡才會跑 BlogModel.OnModelCreating()
    •     }
    • }
  • 執行程式, 會產生第一版的 DB
  • 在 Package Manager Console 裡, 下達  PM> Enable-Migrations
  • • 
    • 在方案總管, 可以看到 Migrations 資料夾的產生.
    • 

• 4. 進行第2次資料庫移轉 (限制欄位長度)

• • 修改 BlogModel.cs
  • • protected override void OnModelCreating(DbModelBuilder modelBuilder)
    • {
    •     var blogTable = modelBuilder.Entity<Blog>().ToTable("Blogs");
    •     var blogArticleTable = modelBuilder.Entity<BlogArticle>().ToTable("BlogArticles");
    •     blogTable.Property(c => c.Id).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.BlogId).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.Subject).HasMaxLength(250).IsRequired();
    •     blogArticleTable.Property(c => c.Body).HasMaxLength(4000).IsRequired();
    •    base.OnModelCreating(modelBuilder);
    • }
  • 在 Package Manager Console 裡, 下達  PM> Add-Migration AlterBlogArticle
  • • 
    • 
    • 
    • • 這裡的 Up() 是資料庫升級用的; Down() 是資料庫降級用的
  • 資料庫還沒有變喔 ...
  • • 
  • 執行 PM> Update-Database
  • • 
  • 終於更改資料庫格式了
  • • 
    • 
      

• 5. 進行第3次資料庫移轉 (加入欄位)  

• • BlogArticle.cs 加入一個 Language 屬性
  • • public class BlogArticle
    • {
    •     public Guid Id { get; set; }
    •     public int BlogId { get; set; }
    •     public string Subject { get; set; }
    •     public string Body { get; set; }
    •     public DateTime DateCreated { get; set; }
    •     public DateTime DateModified { get; set; }
    •     public string Language { get; set; }
    • }
  • PM> Add-Migration AlterBlogArticle
  • 此時, Console 專案會自動建置
  • 
  • PM> Update-Database
  • 
  • 
  • 
    

• 6. 進行第4次資料庫移轉 ( 加入一對無或一的關係 )

• • 加入 BlogInfo.cs
  • • public class BlogInfo
    • {
    •     public Guid Id { get; set; }
    •     public string Author { get; set; }
    •     // 每 1 筆 BlogInfo, 會有 1 筆 Blog (也有可能是 0 筆, 由程式決定)
    •     public Blog Blog { get; set; }
    • }
  • 修改 Blog.cs
  • • public class Blog
    • {
    •     public int Id { get; set; }
    •     public Guid OwnerId { get; set; }
    •     public string Caption { get; set; }
    •     public DateTime DateCreated { get; set; }
    •     // 每 1 筆 Blog, 會有 1 筆 BlogInfo
    •     public BlogInfo Info { get; set; }
    • }
  • 修改 BlogModel.cs
  • • public virtual DbSet<BlogInfo> BlogInfos { get; set; }
    •  
    • protected override void OnModelCreating(DbModelBuilder modelBuilder)
    • {
    •     var blogTable = modelBuilder.Entity<Blog>().ToTable("Blogs");
    •     var blogArticleTable = modelBuilder.Entity<BlogArticle>().ToTable("BlogArticles");
    •     var blogInfoTable = modelBuilder.Entity<BlogInfo>().ToTable("BlogInfos");
    •     // ================================
    •     // 修改資料庫對應的 DataType
    •     // ================================
    •     blogTable.Property(c => c.Id).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.BlogId).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.Subject).HasMaxLength(250).IsRequired();
    •     blogArticleTable.Property(c => c.Body).HasMaxLength(4000).IsRequired();
    •     // ================================
    •     // 建立關聯性
    •     // ================================
    •     // PKEY
    •     blogTable.HasKey(c => c.Id);   
    •     // --------------------------------
    •     // BlogInfos vs. Blogs = 1 vs. 0 or 1
    •     // --------------------------------
    •     //blogTable.HasRequired(c => c.Info).WithOptional();
    •     //http://www.entityframeworktutorial.net/code-first/configure-one-to-one-relationship-in-code-first.aspx
    •     blogInfoTable.HasOptional(c => c.Blog)         // blogInfo has blog -> Optional
    •                            .WithRequired(a => a.Info);       // blog has blogInfo -> Required
    • 
      
    •     base.OnModelCreating(modelBuilder);
    • }
  • PM> Add-Migration AlterOneToOneRelation
  • 
  • PM> Update-Database
  • 
  • 修改  Program.cs 的 MyDbInitializer 類別
  • • class MyDbInitializer : IDatabaseInitializer<BlogModel>
    • {
    •  
    •     private void OneToZero(BlogModel context)
    •     {
    •         // ---------------------------------
    •         // 1 to 0 or 1
    •         // ---------------------------------
    •         Guid blogInfoId = Guid.NewGuid();
    •         context.BlogInfos.Add(new BlogInfo()
    •         {
    •             Id = blogInfoId,
    •             Author = "Judy",
    •             Blog = null
    •         });
    •         blogInfoId = Guid.NewGuid();
    •         context.BlogInfos.Add(new BlogInfo()
    •         {
    •             Id = blogInfoId,
    •             Author = "Jasper",
    •             Blog = new Blog() { Id = 1, Caption = "Travel Blog Site", OwnerId = Guid.NewGuid(), DateCreated = DateTime.Now }
    •         });
    •     }
    • 
      
    •     public void InitializeDatabase(BlogModel context)
    •     {
    •         //context.Database.Delete();
    •         context.Database.CreateIfNotExists();
    •         //以下放一些初始資料新增
    •         // ---------------------------------
    •         // 1 to 0 or 1
    •         // ---------------------------------
    •         this.OneToZero(context);
    • 
      
  •         context.SaveChanges();
  •     }
  • }
• 執行程式
• 註: 還原至某一個版本 (http://stackoverflow.com/questions/11904571/ef-migrations-rollback-last-applied-migration)
• • PM> Update-Database -TargetMigration:"AlterBlogArticle1"

• 7. 進行第5次資料庫移轉 ( 加入一對一的關係 )

• • 修改 BlogModel.cs
  • • public virtual DbSet<BlogInfo> BlogInfos { get; set; }
    • 
      
    • protected override void OnModelCreating(DbModelBuilder modelBuilder)
    • {
    •     var blogTable = modelBuilder.Entity<Blog>().ToTable("Blogs");
    •     var blogArticleTable = modelBuilder.Entity<BlogArticle>().ToTable("BlogArticles");
    •     var blogInfoTable = modelBuilder.Entity<BlogInfo>().ToTable("BlogInfos");
    •     // ================================
    •     // 修改資料庫對應的 DataType
    •     // ================================
    •     blogTable.Property(c => c.Id).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.BlogId).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.Subject).HasMaxLength(250).IsRequired();
    •     blogArticleTable.Property(c => c.Body).HasMaxLength(4000).IsRequired();
    •     // ================================
    •     // 建立關聯性
    •     // ================================
    •     // PKEY
    •     blogTable.HasKey(c => c.Id);
    •     blogInfoTable.HasKey(c => c.Id);
    • 
      
    •     //// --------------------------------
    •     //// BlogInfos vs. Blogs = 1 vs. 0 or 1
    •     //// --------------------------------
    •     ////blogTable.HasRequired(c => c.Info).WithOptional();
    •     //blogInfoTable.HasOptional(c => c.Blog)  // blogInfo has blog -> Optional
    •     //    .WithRequired(a => a.Info);         // blog has blogInfo -> Required
    • 
      
    •     // --------------------------------
    •     // BlogInfos vs. Blogs = 1 vs. 1
    •     // --------------------------------
    •     //blogTable.HasRequired(c => c.Info).WithRequiredPrincipal(c => c.Blog);
    •     blogInfoTable.HasRequired(c => c.Blog)      // blogInfo has blog -> Required
    •         .WithRequiredPrincipal(a => a.Info);    // blog has blogInfo -> Required
    • 
      
    •     base.OnModelCreating(modelBuilder);
    • }
  • 
    
  • PM> Add-Migration AlterOneToOneRelation2
  • 
  • PM> Update-Database
  • 
  • 修改  Program.cs 的 MyDbInitializer 類別
  • •  
    • private void OneToOne(BlogModel context)
    • {
    •     // ---------------------------------
    •     // 1 to 1
    •     // ---------------------------------
    •     Guid blogInfoId = Guid.NewGuid();
    •     context.BlogInfos.Add(new BlogInfo()
    •     {
    •         Id = blogInfoId,
    •         Author = "Jasper",
    •         Blog = new Blog() { Id = 2, Caption = "Travel Blog Site2", OwnerId = Guid.NewGuid(), DateCreated = DateTime.Now }
    •     });
    • }
    •  
    • public void InitializeDatabase(BlogModel context)
    • {
    •     //context.Database.Delete();
    •     context.Database.CreateIfNotExists();
    •     //以下放一些初始資料新增
    •     //// ---------------------------------
    •     //// 1 to 0 or 1
    •     //// ---------------------------------
    •     //this.OneToZero(context);
    •    
    •     // ---------------------------------
    •     // 1 to 1
    •     // ---------------------------------
    •     this.OneToOne(context);
    • 
      
    •     context.SaveChanges();
    • }
  • 執行程式
  • 
    

• 8. 進行第6次資料庫移轉 ( 加入一對多的關係 )

• • 修改 Blog.cs
  • • public class Blog
    • {
    •     public int Id { get; set; }
    •     public Guid OwnerId { get; set; }
    •     public string Caption { get; set; }
    •     public DateTime DateCreated { get; set; }
    •     // 每 1 筆 Blog, 會有 1 筆 BlogInfo
    •     public BlogInfo Info { get; set; }
    •     // 每一個 Blog Site, 會有多篇文章
    •     public ICollection<BlogArticle> Articles { get; set; }
    • }
  • 修改 BlogArticle.cs
  • • public class BlogArticle
    • {
    •     public Guid Id { get; set; }
    •     public int BlogId { get; set; }
    •     public string Subject { get; set; }
    •     public string Body { get; set; }
    •     public DateTime DateCreated { get; set; }
    •     public DateTime DateModified { get; set; }
    •     public string Language { get; set; }
    •     // 每一篇文章都屬於一個 Blog Site
    •     public Blog Blog { get; set; }
    • }
  • 修改 BlogModel.cs
  • • protected override void OnModelCreating(DbModelBuilder modelBuilder)
    • {
    •     var blogTable = modelBuilder.Entity<Blog>().ToTable("Blogs");
    •     var blogArticleTable = modelBuilder.Entity<BlogArticle>().ToTable("BlogArticles");
    •     var blogInfoTable = modelBuilder.Entity<BlogInfo>().ToTable("BlogInfos");
    •     // ================================
    •     // 修改資料庫對應的 DataType
    •     // ================================
    •     blogTable.Property(c => c.Id).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.BlogId).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.Subject).HasMaxLength(250).IsRequired();
    •     blogArticleTable.Property(c => c.Body).HasMaxLength(4000).IsRequired();
    •     // ================================
    •     // 建立關聯性
    •     // ================================
    •     // PKEY
    •     blogTable.HasKey(c => c.Id);
    •     blogInfoTable.HasKey(c => c.Id);
    • 
      
    •     //// --------------------------------
    •     //// BlogInfos vs. Blogs = 1 vs. 0 or 1
    •     //// --------------------------------
    •     ////blogTable.HasRequired(c => c.Info).WithOptional();
    •     //blogInfoTable.HasOptional(c => c.Blog)  // blogInfo has blog -> Optional
    •     //    .WithRequired(a => a.Info);         // blog has blogInfo -> Required
    • 
      
    •     // --------------------------------
    •     // BlogInfos vs. Blogs = 1 vs. 1
    •     // --------------------------------
    •     //blogTable.HasRequired(c => c.Info).WithRequiredPrincipal(c => c.Blog);
    •     blogInfoTable.HasRequired(c => c.Blog)      // blogInfo has blog -> Required
    •         .WithRequiredPrincipal(a => a.Info);    // blog has blogInfo -> Required
    • 
      
    •     // --------------------------------
    •     // Blogs vs. BlogArticles = 1 vs. n
    •     // --------------------------------
    •     blogTable.HasMany(c => c.Articles)      // Blog has many Articles -> Required
    •         .WithRequired(a => a.Blog);         // Articles has Blog -> Required
    • 
      
    •     base.OnModelCreating(modelBuilder);
    • }
  • PM> Add-Migration AlterOneToManyRelation
  • 
  • PM> Update-Database
  • 
  • 修改  Program.cs 的 MyDbInitializer 類別
  • • private void OneToMany(BlogModel context)
    • {
    •     // ---------------------------------
    •     // 1 to n
    •     // ---------------------------------
    •     Guid blogInfoId = Guid.NewGuid();
    •     context.BlogInfos.Add(new BlogInfo()
    •     {
    •         Id = blogInfoId,
    •         Author = "Jasper",
    •         Blog = new Blog()
    •         {
    •             Id = 3,
    •             Caption = "Travel Blog Site3",
    •             OwnerId = Guid.NewGuid(),
    •             DateCreated = DateTime.Now,
    •             Articles = new List<BlogArticle>()
    •             {
    •                 new BlogArticle() { Id = Guid.NewGuid(), BlogId = 3, Subject = "Japan", Body = "Tokyo", Language="中文", DateCreated = DateTime.Now, DateModified = DateTime.Now },
    •                 new BlogArticle() { Id = Guid.NewGuid(), BlogId = 3, Subject = "Japan", Body = "Kyoto", Language="中文", DateCreated = DateTime.Now, DateModified = DateTime.Now }
    •             }
    •         }
    •     });
    • }
    • 
      
    • public void InitializeDatabase(BlogModel context)
    • {
    •     //context.Database.Delete();
    •     context.Database.CreateIfNotExists();
    •     //以下放一些初始資料新增
    • 
      
    •     //// ---------------------------------
    •     //// 1 to 0 or 1
    •     //// ---------------------------------
    •     //this.OneToZero(context);
    • 
      
    •     //// ---------------------------------
    •     //// 1 to 1
    •     //// ---------------------------------
    •     //this.OneToOne(context);
    • 
      
    •     // ---------------------------------
    •     // 1 to n
    •     // ---------------------------------
    •     this.OneToMany(context);
    • 
      
    •     context.SaveChanges();
    • }
  • 執行程式

• 9. 進行第7次資料庫移轉 ( 加入多對多的關係 )

• • 加入 BlogFile.cs 
  • 1個檔案 (BlogFile), 可以被篇文章 (BlogArticle) 使用; 1篇文章 (BlogArticle), 可以包含多個檔案 (BlogFile)
  • • public class BlogFile
    • {
    •     public Guid Id { get; set; }
    •     public string Name { get; set; }
    •     //1個檔案, 可以被篇文章 (article) 使用
    •     public ICollection<BlogArticle> Articles { get; set; }
    • }
  • 修改 BlogArticle.cs
  • • public class BlogArticle
    • {
    •     public Guid Id { get; set; }
    •     public int BlogId { get; set; }
    •     public string Subject { get; set; }
    •     public string Body { get; set; }
    •     public DateTime DateCreated { get; set; }
    •     public DateTime DateModified { get; set; }
    •     public string Language { get; set; }
    •     // 每一篇文章都屬於一個 Blog Site
    •     public Blog Blog { get; set; }
    •     //1篇文章, 可以包含多個檔案
    •     public ICollection<BlogFile> Files { get; set; }
    • }
  • 修改 BlogModel.cs
  • • public virtual DbSet<BlogFile> BlogFiles { get; set; }
    • protected override void OnModelCreating(DbModelBuilder modelBuilder)
    • {
    •     var blogTable = modelBuilder.Entity<Blog>().ToTable("Blogs");
    •     var blogArticleTable = modelBuilder.Entity<BlogArticle>().ToTable("BlogArticles");
    •     var blogInfoTable = modelBuilder.Entity<BlogInfo>().ToTable("BlogInfos");
    •     var blogFileTable = modelBuilder.Entity<BlogFile>().ToTable("BlogFiles");
    •     // ================================
    •     // 修改資料庫對應的 DataType
    •     // ================================
    •     blogTable.Property(c => c.Id).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.BlogId).IsRequired().HasColumnType("bigint");
    •     blogArticleTable.Property(c => c.Subject).HasMaxLength(250).IsRequired();
    •     blogArticleTable.Property(c => c.Body).HasMaxLength(4000).IsRequired();
    • 
      
    •     // ================================
    •     // 建立關聯性
    •     // ================================
    •     // PKEY
    •     blogTable.HasKey(c => c.Id);
    •     blogInfoTable.HasKey(c => c.Id);
    •     blogFileTable.HasKey(c => c.Id);
    • 
      
    •     //// --------------------------------
    •     //// BlogInfos vs. Blogs = 1 vs. 0 or 1
    •     //// --------------------------------
    •     ////blogTable.HasRequired(c => c.Info).WithOptional();
    •     //blogInfoTable.HasOptional(c => c.Blog)  // blogInfo has blog -> Optional
    •     //    .WithRequired(a => a.Info);         // blog has blogInfo -> Required
    • 
      
    •     // --------------------------------
    •     // BlogInfos vs. Blogs = 1 vs. 1
    •     // --------------------------------
    •     //blogTable.HasRequired(c => c.Info).WithRequiredPrincipal(c => c.Blog);
    •     blogInfoTable.HasRequired(c => c.Blog)      // blogInfo has blog -> Required
    •         .WithRequiredPrincipal(a => a.Info);    // blog has blogInfo -> Required
    • 
      
    •     // --------------------------------
    •     // Blogs vs. BlogArticles = 1 vs. n
    •     // --------------------------------
    •     blogTable.HasMany(c => c.Articles)      // Blog has many Articles -> Required
    •         .WithRequired(a => a.Blog);         // Articles has Blog -> Required
    • 
      
    •     // --------------------------------
    •     // BlogArticles vs. BlogFiles = m vs. n
    •     // --------------------------------
    •     // 多對多: 在關聯式資料庫不存在, 會多產生一個 Table, 內含雙方的 PKey, 以造成 2 個 一對多 的關係
    •     blogArticleTable.HasMany(c => c.Files)      // BlogArticle has many BlogFile -> Required
    •         .WithMany(a => a.Articles)         // BlogFile has many BlogAritcle -> Required
    •         .Map
    •         ( m =>
    •             {
    •                 m.ToTable("BlogArticlesFiles");
    •                 m.MapLeftKey("BlogArticlesId");
    •                 m.MapRightKey("BlogFilesId");
    •             }
    •         );
    • 
      
    •     base.OnModelCreating(modelBuilder);
    • }
  • PM> Add-Migration AlterManyToManyRelation
  • 
  • PM> Update-Database
  • 
  • • BlogArticlesFiles 出現了
    • 
  • 修改  Program.cs 的 MyDbInitializer 類別
  • • private void ManyToMany(BlogModel context)
    • {
    •     // ---------------------------------
    •     // m to n
    •     // ---------------------------------
    •     Guid blogInfoId = Guid.NewGuid();
    •     //建立多個檔案
    •     BlogFile file1 = new BlogFile() { Id = Guid.NewGuid(), Name = "BMP檔" };
    •     BlogFile file2 = new BlogFile() { Id = Guid.NewGuid(), Name = "JPG檔" };
    •     BlogFile file3 = new BlogFile() { Id = Guid.NewGuid(), Name = "TXT檔" };
    •     context.BlogInfos.Add(new BlogInfo()
    •     {
    •         Id = blogInfoId,
    •         Author = "Jasper",
    •         Blog = new Blog()
    •         {
    •             Id = 4,
    •             Caption = "Travel Blog Site4",
    •             OwnerId = Guid.NewGuid(),
    •             DateCreated = DateTime.Now,
    •             Articles = new List<BlogArticle>()
    •             {
    •                 new BlogArticle() { Id = Guid.NewGuid(), BlogId = 4, Subject = "Taiwan", Body = "Taipei", Language="中文", DateCreated = DateTime.Now, DateModified = DateTime.Now,
    •                         Files = new List<BlogFile>(){ file1, file2 }  },
    •                 new BlogArticle() { Id = Guid.NewGuid(), BlogId = 4, Subject = "Taiwan", Body = "Tainan", Language="中文", DateCreated = DateTime.Now, DateModified = DateTime.Now,
    •                         Files = new List<BlogFile>(){ file2, file3 }  },
    •                 new BlogArticle() { Id = Guid.NewGuid(), BlogId = 4, Subject = "Taiwan", Body = "Taoyuan", Language="中文", DateCreated = DateTime.Now, DateModified = DateTime.Now,
    •                         Files = new List<BlogFile>(){ file3, file1 }  }
    •             }
    •         }
    •     });
    • }
    • 
      
    • public void InitializeDatabase(BlogModel context)
    • {
    •     //context.Database.Delete();
    •     context.Database.CreateIfNotExists();
    • 
      
    •     //以下放一些初始資料新增
    • 
      
    •     //// ---------------------------------
    •     //// 1 to 0 or 1
    •     //// ---------------------------------
    •     //this.OneToZero(context);
    • 
      
    •     //// ---------------------------------
    •     //// 1 to 1
    •     //// ---------------------------------
    •     //this.OneToOne(context);
    • 
      
    •     //// ---------------------------------
    •     //// 1 to n
    •     //// ---------------------------------
    •     //this.OneToMany(context);
    • 
      
    •     // ---------------------------------
    •     // m to n
    •     // ---------------------------------
    •     this.ManyToMany(context);
    • 
      
    •     context.SaveChanges();
    • }
  • 執行程式

參考文件

• 許薰尹: 使用Entity-Framework-6-Code-First與新資料庫建立應用程式
• Code First for New Database

• 許薰尹: 使用EntityFramework 6 Code First與既有資料庫建立應用程式
• Code First from Existing Database

• Entity Framework Tutorial: Entity Relationships
• 介紹 Entity 之間的關聯性
• 1 to 1
• 1 to many
• many to many

• Entity Framework Tutorial: Configure One-to-One Relationship
• 如何設置 1 to 1 的關聯 (Code First)

• Entity Framework Tutorial: Configure One-to-Many Relationship
• 如何設置 1 to many 的關聯 (Code First)

• Entity Framework Tutorial: Configure Many-to-Many Relationship
• 如何設置 many to many 的關聯 (Code First)

• Entity Framework Tutorial: Add New Entity using DBContext in Disconnected Scenario

• Entity Framework Tutorial: Update Existing Entity using DBContext in Disconnected Scenario

• Entity Framework Tutorial: Delete Entity using DBContext in Disconnected Scenario

• Code Project: Create Primary Key using Entity Framework Code First
• 在 Code First 的狀況下, 共有以下3種方式, 可以設定主鍵 (Primary Key):
• Convention: Property with name "Id" or property with name {class name} + "Id" (both are case insensitive)
• Data Annotation: [Key] attribute
• Fluent API: Entity<T>.HasKey(p => p.PropertyName) function
• 以下為複合鍵 (Composite Key) 的設定範例     

// Data Annotation Attribute 

  public class Passport

    {
       [Key]
       [Column(Order = 10)]
       public string PassportNumber { get; set; }

       [Key]
       [Column(Order = 20)]
       public string CountryCode { get; set; } 

    }

// Fluent API

modelBuilder.Entity<Passport>().HasKey(s => new { s.PassportNumber, s.CountryCode});

• Stack Overflow: Mapping composite keys using EF code first