1.2 Write a simple OData V4 service

Let’s get started by creating a simple OData V4 service. It has one entity set Products, one entity type Product. Product has two properties ID and Name, with ID being an integer and Name being a string. The service is read only. The only data clients can get besides the service document and metadata document, is the Products entity set.

a. Create the Visual Studio project

In Visual Studio, create a new C# project from the ASP.NET Web Application template. Name the project “ODataService”.

In the New Project dialog, select the Empty template. Under “Add folders and core references…”, click Web API. Click OK.

b. Install the OData packages

In the Nuget Package Manager, install Microsoft.AspNet.OData and all it’s dependencies.

c. Add a model class

Add a C# class to the Models folder:

namespace ODataService.Models
{
    public class Product
    {
        public int ID { get; set; }
        public string Name { get; set; }
    }
}

d. Add a controller class

Add a C# class to the Controllers folder:

namespace ODataService.Controllers
{
    public class ProductsController : ODataController
    {
        private List<Product> products = new List<Product>()
        {
            new Product()
            {
                ID = 1,
                Name = "Bread",
            }
        };

        public List<Product> Get()
        {
            return products;
        }
    }
}

In the controller, we defined a List<Product> object which has one product element. It’s considered as a in-memory storage of the data of the OData service.

We also defined a Get method that returns the list of products. The method refers to the handling of HTTP GET requests. We’ll cover that in the sections about routing.

e. Configure the OData Endpoint

Open the file App_Start/WebApiConfig.cs. Replace the existing Register method with the following code:

public static void Register(HttpConfiguration config)
{
    var builder = new ODataConventionModelBuilder();

    builder.EntitySet<Product>("Products");

    config.MapODataServiceRoute("ODataRoute", null, builder.GetEdmModel());
}

f. Start the OData service

Start the OData service by running the project and open a browser to consume it. You should be able to get access to the service document at http://host/service/ in which http://host/service/ is the root path of your service. The metadata document can be accessed at GET http://host/service/$metadata and the products at GET http://host/service/Products.