I have the following project structure I would like to implement. I would like to know if there are any pitfalls to structuring my code this way. It is going to be using Microsoft’s WebAPI, an MVC 4 project, and Plain Old C# Objects (POCO). The explanation follows.

First off there is going to be a class library project that contains only interfaces and objects like so:

public interface IBookService {
   IEnumerable<Book> GetBooks();
}

public class Book {
   public int Id { get; set; }
   public string Name { get; set; }
}

This interface and class will be shared by the other projects. The first being the implementation project which contains:

public class BookService : IBookService {
  // implementation that pulls books from somewhere
}

The third project is going to be a WebAPI project that exposes IBookService as a uri, such as http://mysite/books. UPDATE: This WebAPI site will be sitting on a different machine than the MVC site.

Now here is where I’m concerned about my implementation choice. The fourth and final project is an MVC 4 application. It will reference only the interfaces and the web api (via HttpContent and friends). I would like to implement the IBookService interface in this project as well. Except in this implementation it would call the WebAPI like so.

public class MvcBookService : IBookService {
   public IEnumerable<Book> GetBooks() {
      var client = new HttpClient(); 
      client.BaseAddress = new Uri("http://mySite"); // would be pulled from config
      client.DefaultRequestHeaders.Accept.Add(
         new MediaTypeWithQualityHeaderValue("application/json"));

      HttpResponseMessage response = client.GetAsync("books").Result; // blocking call
      if (response.IsSuccessStatusCode) {
          // blocking call
          return response.Content.ReadAsAsync<IEnumerable<Book>>().Result;
      } else {
         // handle response code
         return null;
      }
   }
}

I plan on enforcing this project structure for all WebAPI interaction within the company.

I don’t for see any maintenance problems with this project layout. However many eyes always helps.