在ASP.NET Web API中使用OData

本文轉載自查看原文 2015-06-26 16:56 5482 OData/ EF/ Web API/ asp.net/ Code First

一.什么是OData
OData是一個開放的數據協議(Open Data Protocol)
在ASP.NET Web API中,
對於CRUD(create, read, update, and delete)應用比傳統WebAPI增加了很大的靈活性
只要正確使用相關的協議，可以在同等情況下
對一個CRUD應用可以節約很多開發時間，從而提高開發效率

二.怎么搭建

做一個簡單的訂單查詢示例
我們使用Code First模式創建兩個實體對象Product(產品),Supplier(供應商)
1.新建一個ASP.NET Empty項目,選擇上使用Web API,如下圖

2.使用NuGet引用OData和EntityFramework程序集

3.在Models文件夾中增加Product(產品),Supplier(供應商)兩個實體

public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
        public string Category { get; set; }
    [ForeignKey(</span><span style="color: #800000">"</span><span style="color: #800000">Supplier</span><span style="color: #800000">"</span><span style="color: #000000">)]
    </span><span style="color: #0000ff">public</span> <span style="color: #0000ff">int</span>? SupplierId { <span style="color: #0000ff">get</span>; <span style="color: #0000ff">set</span><span style="color: #000000">; }
    </span><span style="color: #0000ff">public</span> <span style="color: #0000ff">virtual</span> Supplier Supplier { <span style="color: #0000ff">get</span>; <span style="color: #0000ff">set</span><span style="color: #000000">; }
}

public class Supplier
 {
 public int Id { get; set; }
 public string Name { get; set; }
 public ICollection<Product> Products { get; set; }
 }

4.增加ProductContext數據庫上下文對象，並且在web.config中配置好ConnectionString

public class ProductContext : DbContext
    {
        public ProductContext()
            : base("Demo")
        { }
        public DbSet<Product> Products { get; set; }
        public DbSet<Supplier> Suppliers { get; set; }
    }

<connectionStrings>
        <add name="Demo" connectionString="Data Source=(localdb)\v11.0; 
        Initial Catalog=Demo; Integrated Security=True; MultipleActiveResultSets=True; 
        AttachDbFilename=|DataDirectory|Demo.mdf"
      providerName="System.Data.SqlClient" />
    </connectionStrings>

5.生成數據庫
我們啟動程序包管理控制台，運行如下3個命令，
把我們Code First生成的實體生成到數據庫
PM> Enable-Migrations
PM> Add-Migration FirstInit
PM> Update-Database
然后我們可以在服務器資源管理器中看到我們生成的數據庫表，如下圖

6.接下來我們在WebApiConfig中注冊我們的OData路由

using Demo2.Models;
using System.Web.OData.Builder;
using System.Web.OData.Extensions;
namespace Demo2
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            ODataModelBuilder builder = new ODataConventionModelBuilder();
            builder.EntitySet<Product>("Products");
            builder.EntitySet<Supplier>("Suppliers");
            config.MapODataServiceRoute("ODataRoute", null, builder.GetEdmModel());
        }
    }
}

7.接下來我們分別為Product和Supplier新建ODataController,

我們在上圖中我們選擇好模型類和數據上下文,
並重復上面兩步為Supplier實體也生成對應的ODataController
注意：由於VS2013的OData模板中OData V3版本的模板，
引用的名稱空間要從V3
using System.Web.Http;
using System.Web.Http.ModelBinding;
using System.Web.Http.OData;
using System.Web.Http.OData.Routing;
修改為V4
using System.Web.Http;
using System.Web.OData;

到此，我們的OData示例程序已經搭建完成，我們在瀏覽器里打開這個項目的時候
會出現如下

{
  "@odata.context":"http://localhost:8914/$metadata","value":[
    {
      "name":"Products","kind":"EntitySet","url":"Products"
    },{
      "name":"Suppliers","kind":"EntitySet","url":"Suppliers"
    }
  ]
}

表示已經搭建成功了

三.怎么使用
由於沒有測試數據，我們開始先在數據庫表里為Products和Suppliers增加一些測試數據


接下來我們看看一些簡單的使用示例
在自動生成的ProductsController和SuppliersController中
已經為我們生成了如下一些Action

所以對於一些增加，修改，刪除，更新我就不做過多示例，
這些都是和WebAPI沒有什么太多區別，
我主要示例的是查詢的使用，不得不說OData已經為我們把查詢功能全做完了
示例1：列出所有Product
URL:http://localhost:8914/Products

{
  "@odata.context":"http://localhost:8914/$metadata#Products","value":[
    {
      "Id":1,"Name":"Products1","Price":100.00,"Category":"Test","SupplierId":1
    },{
      "Id":2,"Name":"Products2","Price":200.00,"Category":"Test","SupplierId":1
    },{
      "Id":3,"Name":"Products3","Price":300.00,"Category":"Test","SupplierId":1
    },{
      "Id":4,"Name":"Products4","Price":400.00,"Category":"P1","SupplierId":2
    },{
      "Id":5,"Name":"Products5","Price":500.00,"Category":"P1","SupplierId":2
    },{
      "Id":6,"Name":"Products6","Price":600.00,"Category":"P1","SupplierId":2
    },{
      "Id":7,"Name":"Products7","Price":700.00,"Category":"P1","SupplierId":2
    },{
      "Id":8,"Name":"Products8","Price":800.00,"Category":"Test","SupplierId":3
    },{
      "Id":9,"Name":"Products9","Price":900.00,"Category":"P1","SupplierId":3
    }
  ]
}

示例2,查詢單個Products
URL:http://localhost:8914/Products(1) 其中(1)為Id

{
  "@odata.context":"http://localhost:8914/$metadata#Products/$entity","Id":1,"Name":"Products1","Price":100.00,"Category":"Test","SupplierId":1
}

示例3,查詢Products,只列出Name,Price例
URL：http://localhost:8914/Products?$select=Name,Price

{
  "@odata.context":"http://localhost:8914/$metadata#Products(Name,Price)","value":[
    {
      "Name":"Products1","Price":100.00
    },{
      "Name":"Products2","Price":200.00
    },{
      "Name":"Products3","Price":300.00
    },{
      "Name":"Products4","Price":400.00
    },{
      "Name":"Products5","Price":500.00
    },{
      "Name":"Products6","Price":600.00
    },{
      "Name":"Products7","Price":700.00
    },{
      "Name":"Products8","Price":800.00
    },{
      "Name":"Products9","Price":900.00
    }
  ]
}

示例5：只列出ID為1的Products，只顯示列Name,Price

URL:http://localhost:8914/Products(1)?$select=Name,Price

{
  "@odata.context":"http://localhost:8914/$metadata#Products(Name,Price)/$entity","Name":"Products1","Price":100.00
}

示例6：列出Products(只有列Name,Price),包括Supplier
URL:http://localhost:8914/Products?$select=Name,Price&$expand=Supplier

{
  "@odata.context":"http://localhost:8914/$metadata#Products(Name,Price,Supplier)","value":[
    {
      "Name":"Products1","Price":100.00,"Supplier":{
        "Id":1,"Name":"Supplier1"
      }
    },{
      "Name":"Products2","Price":200.00,"Supplier":{
        "Id":1,"Name":"Supplier1"
      }
    },{
      "Name":"Products3","Price":300.00,"Supplier":{
        "Id":1,"Name":"Supplier1"
      }
    },{
      "Name":"Products4","Price":400.00,"Supplier":{
        "Id":2,"Name":"Supplier2"
      }
    },{
      "Name":"Products5","Price":500.00,"Supplier":{
        "Id":2,"Name":"Supplier2"
      }
    },{
      "Name":"Products6","Price":600.00,"Supplier":{
        "Id":2,"Name":"Supplier2"
      }
    },{
      "Name":"Products7","Price":700.00,"Supplier":{
        "Id":2,"Name":"Supplier2"
      }
    },{
      "Name":"Products8","Price":800.00,"Supplier":{
        "Id":3,"Name":"Supplier3"
      }
    },{
      "Name":"Products9","Price":900.00,"Supplier":{
        "Id":3,"Name":"Supplier3"
      }
    }
  ]
}

示例7:過濾Products,只顯示分類為Test的數據
URL:http://localhost:8914/Products?$filter=Category eq ’Test‘

{
  "@odata.context":"http://localhost:8914/$metadata#Products","value":[
    {
      "Id":1,"Name":"Products1","Price":100.00,"Category":"Test","SupplierId":1
    },{
      "Id":2,"Name":"Products2","Price":200.00,"Category":"Test","SupplierId":1
    },{
      "Id":3,"Name":"Products3","Price":300.00,"Category":"Test","SupplierId":1
    },{
      "Id":8,"Name":"Products8","Price":800.00,"Category":"Test","SupplierId":3
    }
  ]
}

示例8:過濾Products,只顯示分類為Test的數據,並排序
URL：http://localhost:8914/Products?$filter=Category eq ’Test‘&$orderby=Price desc

{
  "@odata.context":"http://localhost:8914/$metadata#Products","value":[
    {
      "Id":8,"Name":"Products8","Price":800.00,"Category":"Test","SupplierId":3
    },{
      "Id":3,"Name":"Products3","Price":300.00,"Category":"Test","SupplierId":1
    },{
      "Id":2,"Name":"Products2","Price":200.00,"Category":"Test","SupplierId":1
    },{
      "Id":1,"Name":"Products1","Price":100.00,"Category":"Test","SupplierId":1
    }
  ]
}

下面是$filter的其它的使用方式
1. http://localhost/Products?$filter=Category eq 'Test'
過濾Category=Test
2.http://localhost/Products?$filter=Price lt 10
過濾Price小於10
3。http://localhost/Products?$filter=Price ge 5 and Price le 15
過濾5<=Price>=15
5,還可以使用數據庫函數如：
$filter=substringof('zz',Name)
$filter=year(ReleaseDate) gt 2005

關於排序
$orderby=Price
$orderby=Price desc
$orderby=Category,Price desc

還有一些過濾器如
$skip，$top,$inlinecount等等
所以OData基本上實現我們們想要查詢的相關方法
對於CURD程序的查詢來說大大提高開發效率

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