ADO.NET Entity Framework on Vs2012 + WCF = Error - wcf

Question

First of all, thanks for reading my question.
I am developing a solution using VS 2012 using ADO.NET Entity Framework (5 i think, the latest version). All is working fine until I introduce a WCF service as a Business Layer (this is an assignment for school, I cannot scrap WCF from Business Layer).
The issue is that when I request data from the database. When I have a method that returns a string from the database, it works just fine (since its a primitive). But when it returns an Entity object (Such as Account), it all goes to hell.
Exception: (Yeah, its very vague).
An error occurred while receiving the HTTP response to http://localhost:8733/Services/AccountsManager. This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down). See server logs for more details.
What I tried: I tried modifying the Entites.tt file to add the [DataContract] [DataMember] Attribute. This is because in the older versions of EF, it seemed to be doing it on its own. But I do not know if this is neccessary since it allows me to compile and does not complain that it is not serializable.
This is how it looks at first:
namespace CommonLayer
{
using System;
using System.Collections.Generic;
public partial class Account
{
public Account()
{
this.Transactions = new HashSet<Transaction>();
this.Transactions1 = new HashSet<Transaction>();
}
public System.Guid ID { get; set; }
public int Type { get; set; }
public string Name { get; set; }
public int Currency { get; set; }
public decimal Balance { get; set; }
public System.DateTime DateOpened { get; set; }
public Nullable<int> Duration { get; set; }
public string UserName { get; set; }
public virtual AccountType AccountType { get; set; }
public virtual Currency Currency1 { get; set; }
public virtual User User { get; set; }
public virtual ICollection<Transaction> Transactions { get; set; }
public virtual ICollection<Transaction> Transactions1 { get; set; }
}
}
How it looks after modification:
namespace CommonLayer
{
using System;
using System.Collections.Generic;
using System.Runtime.Serialization;
[DataContract] public partial class Account
{
public Account()
{
this.Transactions = new HashSet<Transaction>();
this.Transactions1 = new HashSet<Transaction>();
}
[DataMember] public System.Guid ID { get; set; }
[DataMember] public int Type { get; set; }
[DataMember] public string Name { get; set; }
[DataMember] public int Currency { get; set; }
[DataMember] public decimal Balance { get; set; }
[DataMember] public System.DateTime DateOpened { get; set; }
[DataMember] public Nullable<int> Duration { get; set; }
[DataMember] public string UserName { get; set; }
public virtual AccountType AccountType { get; set; }
public virtual Currency Currency1 { get; set; }
public virtual User User { get; set; }
public virtual ICollection<Transaction> Transactions { get; set; }
public virtual ICollection<Transaction> Transactions1 { get; set; }
}
}
Any pointers are greatly appreciated.
My WCF Class
using System;
using System.Collections.Generic;
using System.Linq;
using System.ServiceModel;
using System.Text;
using System.Threading.Tasks;
namespace BusinessLayer
{
[ServiceContract]
interface IAccountsManager
{
[OperationContract]
List<CommonLayer.Account> GetAccounts(String UserName);
[OperationContract]
String GetData();
[OperationContract]
CommonLayer.Account GetAccount(String UserName);
}
class AccountsManager: IAccountsManager, IDisposable
{
public List<CommonLayer.Account> GetAccounts(String UserName)
{
return DataLayer.AccountsRepository.Instance.GetAccountList(UserName).ToList();
}
public String GetData()
{
CommonLayer.Account acc = this.GetAccounts("test").FirstOrDefault();
return acc.DateOpened.ToString();
}
public CommonLayer.Account GetAccount(String UserName)
{
return this.GetAccounts(UserName).FirstOrDefault();
}
public void Dispose()
{
DataLayer.AccountsRepository.Reset();
}
}
}

Answer 1

You need to use a DTO (Data Transfer Object) and map from your EF object to your DTO.
So the service might accept an object called MyDto looking like:
[DataContract]
public class MyDto {
[DataMember]
public int Id {get;set;}
}
and a static mapping class with methods
public static MyEntity Map(MyDto dto) {
return new MyEntity { Id = dto.Id };
}
public static MyDto Map(MyEntity entity) {
return new MyDto { Id = entity.Id };
}
You can then map as required so that the service can use the DTO and Entity Framework can use the Entity.

Answer 2

It seems that when the EF class has Navigation properties (like ICollection<Transaction> Transactions in your class) it will fails when being transferred over WCF.
After many searches I could not find any solution except mapping an EF class into equivalent DTO class that is exactly the same as the EF class except the Navigation propertis and the constructor (i.e. I have stripped all virtual propertis (like ICollection ones) and the ctor from the EF class and have created from that a new class called the same as my EF class plus Dto suffix (e.g. CustomerDto).
I've used AutoMapper to automatically map an EF object into Dto-equivalent one. E.g:
var customer = getCustomer(cid);
var customerDto = Mapper.Map<CustomerDto>(customer);
return customerDto;
My WCF contract includes
[OperationContract]
CustomerDto getCustomerData(int cid);
In addition I needed to do one time initialization of the Mapper. I've done it within Global.asax as follows:
Mapper.CreateMap<Customer, CustomerDto>();

Answer 3

What I have done is changed my Entities.Edmx file. Firstly, I deleted all (2) ".tt" files. Then i changed Code Generation Strategy from None to Default. This seemed to solve all my problems.