OData v4 - Web API 輕量級應用（無Entity Framwork）

本文講述的是簡單的Web API OData使用。一般的，OData應用需要使用到Entity Framwork和database server來實作datasource，在本文中，為了快速的實作OData service，本文使用了in-memory data作為datasource。以下是建立過程。

solution 全覽

建立solution

File->new>Project>Web->Web Application  重命名

安裝NuGet包

• 方法一：運作tools->NuGet package manager->Package manager console

PM> Install-Package Microsoft.AspNet.OData
           

• 方法二：solution下面的References右鍵Manage NuGet packages ，online查詢并安裝odata應用包

建立Models

在Models檔案夾下建立兩個model class， 分别是Person.cs 和Trip.cs，其中Person model能夠前往（navigate to）Trips.

public class Person
    {
        [Key] //from System.ComponentModel.DataAnnotations meaning the property is key
        public String ID { get; set; }
        [Required]  // from System.ComponentModel.DataAnnotations meaning the property is required seperately.
        public String Name { get; set; }
        public String Description { get; set; }
        public List<Trip> Trips { get; set; }
    }
           

public class Trip
    {
        [Key]
        public String ID { get; set; }
        [Required]
        public String Name { get; set; }
    }
           

In-Memory dataSource實作

添加DataSource file->添加DemoDataSources.cs

public class DemoDataSources
    {
        private static DemoDataSources instance = null;
        public static DemoDataSources Instance
        {
            get { return instance ?? (instance = new DemoDataSources()); }
        }
        public List<Person> People { get; set; }
        public List<Trip> Trips { get; set; }
        private DemoDataSources()
        {
            this.Reset();
            this.Initialize();
        }
        public void Reset()
        {
            this.People = new List<Person>();
            this.Trips = new List<Trip>();
        }
        public void Initialize()
        {  //initialize trips
            this.Trips.AddRange(new List<Trip>(){
                new Trip(){
                    ID = "0",
                    Name = "Trip 0"
                },
                new Trip(){
                    ID = "1",
                    Name = "Trip 1"
                },
                new Trip(){
                    ID = "2",
                    Name = "Trip 2"
                }
            });
            //initialize people
            this.People.AddRange(new List<Person>(){
                new Person(){
                    ID = "001",
                    Name = "Demi",
                    Trips = new List<Trip>{Trips[0], Trips[1]}
                },
                new Person(){
                    ID = "002",
                    Name = "Claire",
                    Description = "This is a beautiful girl!",
                    Trips = new List<Trip>{Trips[1], Trips[2],Trips[0]}
                }
            });
        }
    }
           

添加controllers

前面model中有兩個entity set（實體集），在這裡我們就需要對應建立兩個controller，分别是PeopleController.cs和TripsController.cs。本文中隻是給出了簡單的Get查詢方法，也可以增加其他的Odata操作方法,并且實作方法與使用EF實作的DataSource中類似。

[EnableQuery]
    public class PeopleController : ODataController
    {
        public IHttpActionResult Get()
        {
            return Ok(DemoDataSources.Instance.People.AsQueryable());
        }
    }
           

[EnableQuery]
    public class TripsController : ODataController
    {
        public IHttpActionResult Get()
        {
            return Ok(DemoDataSources.Instance.Trips.AsQueryable());
        }
    }
           

配置endpoint

public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services

            // Web API routes
            //config.MapHttpAttributeRoutes();

            //config.Routes.MapHttpRoute(
                //name: "DefaultApi",
                //routeTemplate: "api/{controller}/{id}",
               // defaults: new { id = RouteParameter.Optional }
            //);

            config.MapODataServiceRoute("odata", null, GetEdmModel(), new DefaultODataBatchHandler(GlobalConfiguration.DefaultServer));
            config.EnsureInitialized();

        }

        private static IEdmModel GetEdmModel()
        {
            var builder = new ODataConventionModelBuilder {Namespace = "Demos", ContainerName = "DefaultContainer"};
            builder.EntitySet<Person>("People");
            builder.EntitySet<Trip>("Trips");
            var edmModel = builder.GetEdmModel();
            return edmModel;
        }
           

運作效果

所有的GET方法

http://localhost:26388 - service document

http://localhost:26388/$metadata - service metadata

http://localhost:26388/People - get all

http://localhost:26388/People?$filter=contains(Description,'girl') - filter

http://localhost:26388/People?$select=Name - select

http://localhost:26388/People?$expand=Trips - expand