EntityFramework用法探索（三）CodeFirst流畅API

Code First Fluent API，使用流畅API来定义模型映射。

同样使用与上文 Database First 模式相同的例子，假设需要设计一个零售系统，我们先构建一个 Customer 类。

  public class Customer
  {
    public long Id { get; set; }
    public string Name { get; set; }
    public string Address { get; set; }
    public string Phone { get; set; }
  }

这次没有使用属性来指定对应表名称、主键等。

使用代码创建影射，

  public class CustomerMap : EntityTypeConfiguration<Customer>
  {
    public CustomerMap()
    {
      // Primary Key
      this.HasKey(t => t.Id);

      // Properties
      this.Property(t => t.Name)
          .IsRequired()
          .HasMaxLength(256);

      this.Property(t => t.Phone)
          .IsRequired()
          .HasMaxLength(256);

      // Table & Column Mappings
      this.ToTable("Customer", "STORE");
      this.Property(t => t.Id).HasColumnName("Id");
      this.Property(t => t.Name).HasColumnName("Name");
      this.Property(t => t.Address).HasColumnName("Address");
      this.Property(t => t.Phone).HasColumnName("Phone");

      // Relationships
      //this.HasRequired(t => t.Status)
      //    .WithMany(t => t.CustomerStatus)
      //    .HasForeignKey(d => d.Status);
    }
  }

在上下文对象中覆写OnModelCreating方法来添加影射配置，

  public class RetailEntities : DbContext
  {
    static RetailEntities()
    {
      //Database.SetInitializer<RetailEntities>(new CreateDatabaseIfNotExists<RetailEntities>());
      //Database.SetInitializer<RetailEntities>(new DropCreateDatabaseAlways<RetailEntities>());
      //Database.SetInitializer<RetailEntities>(new DropCreateDatabaseIfModelChanges<RetailEntities>());
      Database.SetInitializer<RetailEntities>(null);
    }

    public RetailEntities()
      : base("Name=RetailEntities")
    {
    }

    public DbSet<Customer> Customers { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
      modelBuilder.Configurations.Add(new CustomerMap());
    }
  }

ICustomerRepository接口和实现依然类似，

    public void InsertCustomer(DomainModels.Customer customer)
    {
      using (RETAILContext context = new RETAILContext())
      {
        Customer entity = Mapper.Map<DomainModels.Customer, Customer>(customer);
        context.Customers.Add(entity);
        context.SaveChanges();

        customer.Id = entity.Id;
      }
    }

    public void UpdateCustomer(DomainModels.Customer customer)
    {
      using (RETAILContext context = new RETAILContext())
      {
        Customer entity = context.Customers.AsQueryable().Single(c => c.Id == customer.Id);

        entity.Name = customer.Name;
        entity.Address = customer.Address;
        entity.Phone = customer.Phone;

        context.SaveChanges();
      }
    }

同样的测试代码，

      ICustomerRepository customerRepository = new CustomerRepository();

      // =============== 增 ===============
      Console.ForegroundColor = ConsoleColor.DarkRed;

      DomainModels.Customer customer1 = new DomainModels.Customer()
      {
        Name = "Dennis Gao",
        Address = "Beijing",
        Phone = "18888888888",
      };
      customerRepository.InsertCustomer(customer1);
      Console.WriteLine(customer1);

当然，你可能觉得手工写影射代码还是比较繁琐，如果已有部分数据表结构，希望反向生成代码，可使用工具 Entity Framework Power Tools 来生成。

Entity Framework Power Tools 拯救程序员啊。

完整代码和索引

EntityFramework用法探索系列

• （一）DatabaseFirst
• （二）CodeFirst
• （三）CodeFirst流畅API
• （四）Repository和UnitOfWork
• （五）引入Unity
• （六）静态Repository
• （七）线程安全实践
• （八）事务处理

完整代码下载