Access Data with REST in Windows 8 Apps

The GroupsController class inherits from System.Wep.Http.ApiController. Because you've chosen the Empty API controller template, there aren't methods defined for the class. A complete REST service would require you to implement the following methods in a simple entity with a numeric ID and a string value:

Because the goal is to retrieve all the groups with their items from the Windows Store app, I focus just on the IEnumerable<Group> Get() method. The following code creates an array of Group with six groups. Only one group has two items, just to keep the example simple. You can add more items to other groups in order to check how the Grid app works in detail.

namespace DrDobbsWebAPI.Controllers
{
    using System.Collections.Generic;
    using System.Linq;
    using System.Web.Http;

    using DrDobbsApp.Entities;

    public class GroupsController : ApiController
    {
        private readonly Group[] _groups = new[]
        {
            new Group
            {
                Id = "1",
                Title = "Cloud",
                Subtitle = "Cloud Developer",
                Description = "Cloud feature articles",
                MainPage = "cloud",
                Items = new[]
                    {
                        new Item
                        {
                            Id = "240012549",
                            Title = "AMD's Bold ARM Server Gambit",
                            Subtitle = "AMD's Bold ARM Server Gambit",
      Description = 
         @"By combining 64-bit ARM processors with server-side " + 
          "technology, the company that led the x86 " +
          "architecture into the 64-bit world is hoping to " +
          "reinvent the data center and give itself new life.",
                            Content = "Content for AMD's Bold ARM Server Gambit...",
                            MainPage = "cloud/amds-bold-arm-server-gambit/240012549"
                        },
                        new Item
                        {
                            Id = "120020304050",
                            Title = "How Atlassian moved a code base of 21,000 files with " +  
                                    "more than 47,000 commits on its best-selling product " +
                                    "from Subversion to Git without " +
                                    "stopping the development workflow.",
                            Subtitle = 
                               "Migrating from Subversion to Git and the Lessons Learned",
                            Description = "It is incredible how the cloud growths",
                            Content = 
                               "Content for Migrating from Subversion to Git and the " + 
                               "Lessons Learned...",
                            MainPage = "cloud/240009175"
                        },
                    }
            },
            new Group
            {
                Id = "2",
                Title = "Mobile",
                Subtitle = "Mobile Developer",
                Description = "Mobile feature articles",
                MainPage = "mobile"
            },
            new Group
            {
                Id = "3",
                Title = "Parallel",
                Subtitle = "Parallel Programming",
                Description = "Parallel feature articles",
                MainPage = "parallel"
            },
            new Group
            {
                Id = "4",
                Title = ".NET",
                Subtitle = "M-Dev",
                Description = "The world of Microsoft Developers",
                MainPage = "windows"
            },
            new Group
            {
                Id = "5",
                Title = "JVM Languages",
                Subtitle = "Powered by Java Virtual Machine",
                Description = "The world of JVM languages",
                MainPage = "jvm"
            },
            new Group
            {
                Id = "6",
                Title = "C/C++",
                Subtitle = "Powered by C/C++",
                Description = "The world of C/++ developers",
                MainPage = "cpp"
            }
        };

        /// <summary>
        /// Retrieves all the groups with their items
        /// GET api/values
        /// </summary>
        /// <returns>All the groups with their items</returns>
        public IEnumerable<Group> Get()
        {
            return _groups.ToArray();
        }
    }
}

Notice that Group is DrDobbsApp.Entities.Group, thus, I'm using the class shared in the previously created PCL. It is really very easy to create a REST service with ASP.NET Web API, and I have a service ready to provide data to my Windows Store app.

Now, I just have to make sure it works correctly. First, it is necessary to check the base URL in the project Web configuration. To do this, right click on DrDobbsWebAPI in Solution Explorer, select Properties | Web and check the value for Project URL in case you're using your local IIS Web Server (see Figure 8).

Figure 8: Web properties for the ASP.NET Web API project with the Project URL details.

In my case, the Project Url is http://localhost:46037/, so I can retrieve the groups if I execute the solution and I enter the following URL in any Web browser: http://localhost:46037/api/groups. I just need to add api/groups to the base URL, as explained in the table. Figure 9 shows the partial results of http://localhost:46037/api/groups that executes the GroupsController.Get method that returns an IEnumerable<Group>.

Figure 9: Using a Web browser to test that the GET api/groups REST call is working OK.

Making Calls to a REST Service with System.Net.Http.HttpClient

Now that I've created the REST service, I'll consume it in the sample Grid app by using the new asynchronous methods provided by the new System.Net.Http.HttpClient. Thus, it is necessary to go back to the DrDobbsApp project and follow these steps: