ASP.NET Web API教程 创建域模型的方法详细介绍

namespace ProductStore.Models 
{ 
using System.ComponentModel.DataAnnotations; 
public class Product 
{ 
[ScaffoldColumn(false)] 
public int Id { get; set; } 
[Required] 
public string Name { get; set; } 
public decimal Price { get; set; } 
public decimal ActualCost { get; set; } 
} 
} 
 
By convention, Entity Framework uses the Id property as the primary key and maps it to an identity column in the database table. When you create a new Product instance, you won't set a value for Id, because the database generates the value. 
根据约定，实体框架用Id属性作为主键，并把它映射成数据库表中的标识列。当创建一个新的Product实例时，不必为Id设置值，因为数据库会生成它。 
The ScaffoldColumn attribute tells ASP.NET MVC to skip the Id property when generating an editor form. The Required attribute is used to validate the model. It specifies that the Name property must be a non-empty string. 
ScaffoldColumn（支架列）注解属性是告诉ASP.NET MVC，在生成编辑表单时，跳过这个Id属性。Required注解属性用于对模型进行验证。它指定Name属性必须是一个非空字符串。 
注：本文把ScaffoldConlumn、Required等这一类英文中叫做Annotation Attribute的属性（Attribute）译为注解属性（Annotation Attribute），以便与类中的那些属性加以区别 — 译者注 
Add the Order class: 
添加Order类（订单类）： 
 代码如下:

namespace ProductStore.Models 
{ 
using System.Collections.Generic; 
using System.ComponentModel.DataAnnotations; 
public class Order 
{ 
public int Id { get; set; } 
[Required] 
public string Customer { get; set; } 
// Navigation property 
// 导航属性 
public ICollection<OrderDetail> OrderDetails { get; set; } 
} 
} 
 
Add the OrderDetail class: 
添加OrderDetail类（订单细节类，或订单详情类）： 
 代码如下:

namespace ProductStore.Models 
{ 
public class OrderDetail 
{ 
public int Id { get; set; } 
public int Quantity { get; set; } 
public int OrderId { get; set; } 
public int ProductId { get; set; } 
// Navigation properties 
public Product Product { get; set; } 
public Order Order { get; set; } 
} 
} 
 
Foreign Key Relations 
外键关系 
An order contains many order details, and each order detail refers to a single product. To represent these relations, the OrderDetail class defines properties named OrderId and ProductId. Entity Framework will infer that these properties represent foreign keys, and will add foreign-key constraints to the database. 
一份订单包含很多订单细节，而每个订单细节指向一个单一的产品。为了表示这些关系，OrderDetail类定义了名称为OrderId和ProductId的属性。实体框架将会推断出这些属性表示的是外键，并会把外键约束添加到数据库（见图2-15）。 
 
图2-15. 外键关系 
The Order and OrderDetail classes also include “navigation” properties, which contain references to the related objects. Given an order, you can navigate to the products in the order by following the navigation properties. 
Order和OrderDetail类也包含了“导航（navigation）”属性，导航属性包含了对相关对象的引用。对于一份给定的订单，可以根据导航属性导航到这份订单的产品。 
Compile the project now. Entity Framework uses reflection to discover the properties of the models, so it requires a compiled assembly to create the database schema. 
现在，编译这个项目。实体框架会使用反射来发现这些模型的属性，因此它需要编译后的程序集来创建相应的数据库方案（这里的数据库方案意指数据库、表结构以及关系等数据库方面的定义 — 译者注）。 
Configure the Media-Type Formatters 
配置Media-Type格式化器 
A media-type formatter is an object that serializes your data when Web API writes the HTTP response body. The built-in formatters support JSON and XML output. By default, both of these formatters serialize all objects by value. 
media-type（媒体类型）格式化器是Web API书写HTTP响应体时对数据进行序列化的一个对象。内建的格式化器支持JSON和XML