ASP.NET Web API教程 創建域模型的方法詳細介紹

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. 
根據約定，實體框架用Id屬性作為主鍵，并把它映射成數據庫表中的標識列。當創建一個新的Product實例時，不必為Id設置值，因為數據庫會生成它。 
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）注解屬性是告訴ASP.NET MVC，在生成編輯表單時，跳過這個Id屬性。Required注解屬性用于對模型進行驗證。它指定Name屬性必須是一個非空字符串。 
注：本文把ScaffoldConlumn、Required等這一類英文中叫做Annotation Attribute的屬性（Attribute）譯為注解屬性（Annotation Attribute），以便與類中的那些屬性加以區別 — 譯者注 
Add the Order class: 
添加Order類（訂單類）： 
 代碼如下:

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 
// 導航屬性 
public ICollection<OrderDetail> OrderDetails { get; set; } 
} 
} 
 
Add the OrderDetail class: 
添加OrderDetail類（訂單細節類，或訂單詳情類）： 
 代碼如下:

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 
外鍵關系 
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. 
一份訂單包含很多訂單細節，而每個訂單細節指向一個單一的產品。為了表示這些關系，OrderDetail類定義了名稱為OrderId和ProductId的屬性。實體框架將會推斷出這些屬性表示的是外鍵，并會把外鍵約束添加到數據庫（見圖2-15）。 
 
圖2-15. 外鍵關系 
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類也包含了“導航（navigation）”屬性，導航屬性包含了對相關對象的引用。對于一份給定的訂單，可以根據導航屬性導航到這份訂單的產品。 
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. 
現在，編譯這個項目。實體框架會使用反射來發現這些模型的屬性，因此它需要編譯后的程序集來創建相應的數據庫方案（這里的數據庫方案意指數據庫、表結構以及關系等數據庫方面的定義 — 譯者注）。 
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（媒體類型）格式化器是Web API書寫HTTP響應體時對數據進行序列化的一個對象。內建的格式化器支持JSON和XML