TinyFrame開篇：基於CodeFirst的ORM

時間 2019-11-30

標籤 tinyframe 開篇基於 codefirst orm 欄目快樂工作简体版

原文原文鏈接

前言html

作項目的這段時間，因爲比較忙，一直沒有機會閒下來思考。正好趁目前手頭活兒輕鬆點，就花了一兩天時間搭建了一個比較簡單的框架，名稱暫時就叫作：TinyFrame吧。顧名思義，就是微框架的意思。雖然這個框架很小，可是包含了ORM，IOC，AOP以及Restful service支持。真所謂麻雀雖小，可是五臟俱全。今天主要講解的就是基於CodeFirst的ORM實現方式。數據庫

在傳統的開發思惟中，咱們通常都是先創建好數據庫，而後佈局各類Model類，最後調用。這種方式被稱爲DbFirst方式，也就是先有DataBase，而後再佈局邏輯。而CodeFirst相反，是先創建好model，創建好須要的字段，而後由EntityFramework來自動生成數據庫的表，看上去有點像DDD的開發方式。app

下面就開始吧。框架

實現步驟解說less

首先，咱們以一個簡易的圖書借閱爲例：在圖書館中，圖書是有分類的，好比屬於計算機類，仍是屬於文學類；圖書是有存放位置的，好比存放於圖書館一樓，仍是二樓；圖書是有自身屬性的，好比圖書名稱，圖書做者等；圖書借閱是須要人來參與的，因此會有學生這個集體；圖書借閱須要知道誰借了什麼書，何時到期等，是須要一個數據存儲中心的。因此，綜上所述，能夠創建以下的Model來。ide

來看看數據關係圖：佈局

這裏能夠看到總共有五張表，他們的Model類建立以下：ui

Book實體類，主要用來描述圖書的自己屬性，一本書只能放置在一個地方，只能屬於一個種類，有BookTypeID和BookPlaceID做爲外鍵約束：this

   1:  namespace BookStore.Data

   2:  {

   3:      public class Book

   4:      {

   5:          public Book()

   6:          {

   7:              BookType = new BookType();

   8:              BookPlace = new BookPlace();

   9:          }

10:

  11:          public int ID { get; set; }

  12:          public string Name { get; set; }

  13:          public string Author { get; set; }

  14:          public string Publishment { get; set; }

  15:          public int BookTypeID { get; set; }

  16:          public int BookPlaceID { get; set; }

17:

  18:          public BookType BookType { get; set; }

  19:          public BookPlace BookPlace { get; set; }

  20:      }

  21:  }

BookLend實體類，主要用來描述哪位學生借閱了什麼書籍，一個學生能夠借閱多本書籍，因此裏面放了一個Student實體類，對應着多個Books，有BookID和StudentID做爲外鍵約束：spa

   1:  namespace BookStore.Data

   2:  {

   3:      public class BookLend

   4:      {

   5:          public BookLend()

   6:          {

   7:              Student = new Student();

   8:              Books = new List<Book>();

   9:          }

  10:          public int ID { get; set; }

  11:          public int LendDays { get; set; }

  12:          public DateTime LendDate { get; set; }

  13:          public int BookID { get; set; }

  14:          public int StudentID { get; set; }

15:

  16:          public IList<Book> Books { get; set; }

  17:          public Student Student { get; set; }

  18:      }

  19:  }

BookPlace實體類，主要用來描述圖書放置的位置：

   1:  namespace BookStore.Data

   2:  {

   3:      public class BookPlace

   4:      {

   5:          public int ID { get; set; }

   6:          public string Position { get; set; }

   7:      }

   8:  }

BookType實體類，主要用來描述圖書種類：

   1:  namespace BookStore.Data

   2:  {

   3:      public class BookType

   4:      {

   5:          public int ID { get; set; }

   6:          public string Name { get; set; }

   7:      }

   8:  }

Student實體類，主要用來描述學生屬性：

   1:  namespace BookStore.Data

   2:  {

   3:      public class Student

   4:      {

   5:          public int ID { get; set; }

   6:          public string Name { get; set; }

   7:          public string Number { get; set; }

   8:          public string Major { get; set; }

   9:          public string TelPhone { get; set; }

  10:          public string Address { get; set; }

  11:          public Gender Gender { get; set; }

  12:      }

  13:  }

這裏還有個附加的枚舉性別選項：

   1:  namespace BookStore.Data

   2:  {

   3:      public enum Gender

   4:      {

   5:          Male = 0,    //男

   6:          Female = 1    //女

   7:      }

   8:  }

到這裏，咱們的Model就建立好了。

而後咱們來建立ModelMapper。這種Mapper主要是用來設置各個字段的屬性的。

BookMapper類：

   1:  namespace BookStore.Data

   2:  {

   3:      public class BookMapper:EntityTypeConfiguration<Book>

   4:      {

   5:          public BookMapper()

   6:          {

   7:              this.ToTable("Book");

8:

   9:              this.HasKey(c => c.ID);

  10:              this.Property(c => c.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

  11:              this.Property(c => c.ID).IsRequired();

12:

  13:              this.Property(c => c.Name).HasMaxLength(255);

  14:              this.Property(c => c.Name).IsRequired();

15:

  16:              this.Property(c => c.Author).HasMaxLength(255);

  17:              this.Property(c => c.Author).IsOptional();

18:

  19:              this.Property(c => c.Publishment).HasMaxLength(255);

  20:              this.Property(c => c.Publishment).IsRequired();

21:

  22:              this.HasRequired(c => c.BookType).WithMany().HasForeignKey(s => s.BookTypeID);

  23:              this.HasRequired(c => c.BookPlace).WithMany().HasForeignKey(s => s.BookPlaceID);

24:

  25:          }

  26:      }

  27:  }

第7行代碼表示：對於Book實體類來講，最終將會在數據庫中爲其建立名稱爲Book的數據表。

第9行代碼表示：這是一個主鍵。

第10行代碼表示：這個主鍵是自增的。

第11行代碼表示：這個主鍵是不能爲空的。

第13，14行代碼表示：這是一個普通屬性，字段最大長度爲255，不能爲空。

第16，17行代碼表示：這是一個普通屬性，字段最大長度爲255，能夠爲空。

第22，23行代碼表示：在BookType表和BookPlace表中存在外鍵依賴。須要注意的是，若是Model類中定義了BookTypeID和BookPlaceID，這裏必定要用HasForeignKey方法來指明。不然，能夠利用Map方法來隱式指定。

接下來的Mapper就不一一解釋了：

BookLendManager類：

   1:  namespace BookStore.Data

   2:  {

   3:      public class BookLendMapper : EntityTypeConfiguration<BookLend>

   4:      {

   5:          public BookLendMapper()

   6:          {

   7:              this.ToTable("BookLend");

8:

   9:              this.HasKey(c=>c.ID);

  10:              this.Property(c => c.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

  11:              this.Property(c => c.ID).IsRequired();

12:

  13:              this.Property(c => c.LendDays).IsRequired();

14:

  15:              this.Property(c => c.LendDate).IsRequired();

  16:              this.Property(s => s.LendDate).HasColumnType("smalldatetime");

17:

  18:              this.HasRequired(c => c.Books).WithMany().HasForeignKey(s=>s.BookID);

  19:              this.HasRequired(c => c.Student).WithMany().HasForeignKey(s =>s.StudentID);

  20:          }

  21:      }

  22:  }

BookPlaceMapper類：

   1:  namespace BookStore.Data

   2:  {

   3:      public class BookPlaceMapper : EntityTypeConfiguration<BookPlace>

   4:      {

   5:          public BookPlaceMapper()

   6:          {

   7:              this.ToTable("BookPlace");

8:

   9:              this.HasKey(c=>c.ID);

  10:              this.Property(c => c.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

  11:              this.Property(c => c.ID).IsRequired();

12:

  13:              this.Property(c => c.Position).IsRequired();

  14:              this.Property(c => c.Position).HasMaxLength(255);

  15:          }

  16:      }

  17:  }

BookTypeMapper類：

   1:  namespace BookStore.Data.Mapper

   2:  {

   3:      public class BookTypeMapper : EntityTypeConfiguration<BookType>

   4:      {

   5:          public BookTypeMapper()

   6:          {

   7:              this.ToTable("BookType");

8:

   9:              this.HasKey(c => c.ID);

  10:              this.Property(c => c.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

  11:              this.Property(c => c.ID).IsRequired();

12:

  13:              this.Property(c => c.Name).IsRequired();

  14:              this.Property(c => c.Name).HasMaxLength(255);

  15:          }

  16:      }

  17:  }

StudentMapper類：

   1:  namespace BookStore.Data

   2:  {

   3:      public class StudentMapper : EntityTypeConfiguration<Student>

   4:      {

   5:          public StudentMapper()

   6:          {

   7:              this.ToTable("Student");

8:

   9:              this.HasKey(c=>c.ID);

  10:              this.Property(c => c.ID).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

  11:              this.Property(c => c.ID).IsRequired();

12:

  13:              this.Property(c => c.Name).IsRequired();

  14:              this.Property(c => c.Name).HasMaxLength(255);

15:

  16:              this.Property(c => c.Number).IsRequired();

  17:              this.Property(c => c.Number).HasMaxLength(12);

18:

  19:              this.Property(c => c.Major).IsOptional();

  20:              this.Property(c => c.Major).HasMaxLength(255);

21:

  22:              this.Property(c => c.Address).IsOptional();

  23:              this.Property(c => c.Address).HasMaxLength(255);

24:

  25:              this.Property(c => c.Gender).IsRequired();

  26:          }

  27:      }

  28:  }

當咱們寫完這些mapper的時候，工做已經完成一大半了，剩下的就是如何將其自動建立到數據庫中的問題了。

這裏咱們須要用到EF的SetInitializer方法：

首先建立一個BookContext，繼承自DbContext類，而後在構造中書寫如下代碼，以便實現數據實體類遷移：

   1:   public BookContext()

   2:              : base("BookConnection")

   3:          {

   4:              Configuration.ProxyCreationEnabled = false;

   5:              Configuration.LazyLoadingEnabled = false;

   6:              Database.SetInitializer(new MigrateDatabaseToLatestVersion<BookContext, BookContextMConfig>());

   7:          }

而後重寫其OnModelCreating方法,將Mapper類加入到ModelBuilder中:

   1:     protected override void OnModelCreating(DbModelBuilder modelBuilder)

   2:          {

   3:              modelBuilder.Configurations.Add(new BookMapper());

   4:              modelBuilder.Configurations.Add(new BookLendMapper());

   5:              modelBuilder.Configurations.Add(new BookTypeMapper());

   6:              modelBuilder.Configurations.Add(new BookPlaceMapper());

   7:              modelBuilder.Configurations.Add(new StudentMapper());

   8:              modelBuilder.Configurations.Add(new ManagerMapper());

   9:              base.OnModelCreating(modelBuilder);

  10:          }

其中須要注意BookContextMConfig這個類,它須要繼承DbMigrationsConfiguration類:

   1:      public class BookContextMConfig : DbMigrationsConfiguration<BookContext>

   2:      {

   3:          public BookContextMConfig()

   4:          {

   5:              this.AutomaticMigrationDataLossAllowed = true;

   6:              this.AutomaticMigrationsEnabled = true;

   7:          }

   8:      }

這樣咱們的一個完整的ORM就封裝好了.經過訪問BookContext對象,咱們就能夠從數據庫得到與之對應的實體類.

最後還要注意，須要將數據庫鏈接寫到配置文件中：

  <connectionStrings>
    <add name="BookConnection" connectionString="server=180-server;database=BookConnection;uid=sa;pwd=*****" providerName="System.Data.SqlClient" />
  </connectionStrings>