Getting 404 response from web api

1. I have webapi and method:

   public class ArticlesController : ApiController
   {
        //
        // GET: api/values
        public IEnumerable<Article> Get()
        {
            using (CollectionsEntities entities = new CollectionsEntities())
            {
                 return entities.Articles.ToList<Article>();
            }
        }
    }
   

It works fine, and check it in browser:

2. I create a client:

   public static class CollectionClient
   {
       private static readonly HttpClient client;
   
       public static Uri ServerBaseUri
       {
           get { return new Uri("http://localhost:10779/api/"); }
       }
   
       public static Boolean IsDirty { get; private set; }
   
       static CollectionClient()
       {
           IsDirty = true;
           client = new HttpClient(new DemoHttpMessageHandler());
       }
   
       // get all articles
       public static async Task<List<Article>> GetAllArticlesAsync()
       {
           client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
           Uri serverUril = new Uri(ServerBaseUri, "Articles");            
           var response = await client.GetAsync(serverUril);
   
           response.EnsureSuccessStatusCode();
   
           var articles = await response.Content.ReadAsAsync<List<Article>>();
           IsDirty = false;
           return articles;   
       }
   }
   

The response gets 404 status code:

ID_CAP_NETWORKING is checked to make sure it can access internet. Could anybody give me a hand? Thanks in advance!