MVC3 - Unity/Unit of Work Pattern and Webservice implementation - asp.net-mvc-3

Question

I am a newbie to with unity and unit of work pattern and I am trying to write a code, which connects to my webservice and does all the work.
Everything goes well until I use the Database but I get lost when I try to use the webservice.
I have wasted my 2 precious days, searching every single possible article related to it and applying it to my code, but no luck till date.
I know, by writing connection string to web.config and calling it in dbcontext class controller will connect to the required database, but I am not connecting to any database, so what changes I need to do in web/app.config. Also, even if I write my connection logic in dbcontext constructor, it still searches and fills the dbcontext with sql server details. I presume thats happening because I am using DBSet.
Guys, you are requested to have a look at my code, I have done and show me some hope that I can do it. Let me know, if you want any other info related to the code that you want to see.
thanks
DBCONTEXT
public class CVSContext : DbContext
{
public DbSet<CVSViewModel> CVS { get; set; }
public DbSet<Contact> Contacts { get; set; }
public DbSet<Account> Accounts { get; set; }
public CVSContext()
{
//CRM Start
var clientCredentials = new System.ServiceModel.Description.ClientCredentials();
clientCredentials.UserName.UserName = "";
clientCredentials.UserName.Password = "";
var serviceProxy = new Microsoft.Xrm.Sdk.Client.OrganizationServiceProxy(new Uri("http://Organization.svc"), null, clientCredentials, null);
serviceProxy.ServiceConfiguration.CurrentServiceEndpoint.Behaviors.Add(new ProxyTypesBehavior());
HttpContext.Current.Session.Add("ServiceProxy", serviceProxy);
//CRM End
}
}
GENERIC REPOSITORY
public class GenericRepository<TEntity> where TEntity : class
{
internal CVSContext context;
internal DbSet<TEntity> dbSet;
public GenericRepository(CVSContext context)
{
this.context = context;
this.dbSet = context.Set<TEntity>();
}
}
UNIT OF WORK
public interface IUnitOfWork : IDisposable
{
int SaveChanges();
}
public interface IDALContext : IUnitOfWork
{
ICVSRepository CVS { get; set; }
IContactRepository Contacts { get; set; }
//IAccountRepository Accounts { get; set; }
}
public class DALContext : IDALContext
{
private CVSContext dbContext;
private ICVSRepository cvs;
private IContactRepository contacts;
// private IAccountRepository accounts;
public DALContext()
{
dbContext = new CVSContext();
}
public ICVSRepository CVS
{
get
{
if (cvs == null)
cvs = new CVSRepository(dbContext);
return cvs;
}
set
{
if (cvs == value)
cvs = value;
}
}
public IContactRepository Contacts
{
get
{
if (contacts == null)
contacts = new ContactRepository(dbContext);
return contacts;
}
set
{
if (contacts == value)
contacts = value;
}
}
public int SaveChanges()
{
return this.SaveChanges();
}
public void Dispose()
{
if(contacts != null)
contacts.Dispose();
//if(accounts != null)
// accounts.Dispose();
if(dbContext != null)
dbContext.Dispose();
GC.SuppressFinalize(this);
}
}
SERVICE
public interface ICVSService
{
Contact CreateContact(Guid contactName, string productName, int price);
List<CVSViewModel> GetCVS();
List<Contact> GetContacts();
List<Account> GetAccounts();
}
public class CVSService : ICVSService, IDisposable
{
private IDALContext context;
public CVSService(IDALContext dal)
{
context = dal;
}
public List<CVSViewModel> GetCVS()
{
return context.CVS.All().ToList();
}
public List<Contact> GetContacts()
{
return context.Contacts.All().ToList();
}
public List<Account> GetAccounts()
{
return context.Accounts.All().ToList();
}
public Contact CreateContact(Guid contactName, string accountName, int price)
{
var contact = new Contact() { ContactId = contactName };
var account = new Account() { ContactName = accountName, Rent = price, Contact = contact };
//context.Contacts.Create(contact);
context.SaveChanges();
return contact;
}
public void Dispose()
{
if (context != null)
context.Dispose();
}
}
CONTROLLER
public ActionResult Index()
{
ViewData.Model = service.GetContacts();
return View();
}

Answer 1

It's all about proper abstractions. The common abstraction that is used between some data source (could be a db or ws) is the Repository pattern, or at a higher level the Unit of Work pattern. In fact Entity Framework DbContext is an implementation of the Unit of Work pattern, but it is tailored for databases. You can't use to communicate with a web service.
In that case you will have to write your own IRepository<T> abstraction and have a database specific implementation that uses a DbContext under the covers and a web service specific implementation that wraps a web service client proxy under the covers.
However, when your application gets more complex, you often find yourself wanting to have some sort of transaction like behavior. This is what the Unit of Work pattern if for: it presents a business transaction. Using the unit of work pattern to wrap multiple WS calls however, will get painful very soon. It's a lot of work to get right and in that case you will be much better of using a message based architecture.
With a message based architecture you define a single atomic operation (a business transaction or use case) as a specific message, for instance:
public class MoveCustomerCommand
{
public int CustomerId { get; set; }
public Address NewAddress { get; set; }
}
This is just an object (DTO) with a set of properties, but without behavior. Nice about this is that you can pass these kinds of objects over the wire using WCF or any other technology or process them locally without the need for the consumer to know.
Take a look at this article that describes it in detail. This article builds on top of that model and describes how you can write highly maintainable WCF services using this model.