如何首先使用带有EF代码的wcf数据服务公开dto对象？

Question

I am trying to make a wcf data service where i dont want to get acces to the database models but instead i want to use Data transfer objects. I have been reading a lot on the internet about how to accomplish this but i cant get a good answer for my problem. It is the first time for me doing something with wcf data services so i am a little inexperienced.

Oke here are my models that are linked to my database using Entity Framework

public class User
    {
        [Key]
        public int UserId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string UserName { get; set; }
        public string Email { get; set; }

        public string CountryCode { get; set; }
        public string PhoneNumber { get; set; }
        public ICollection<User> Contacts { get; set; }

        public virtual Language Language { get; set; }

        public User()
        {
            Contacts = new List<User>();
        }
    }

public class Message
    {
        [Key]
        public int MessageId { get; set; }
        public DateTime SentDate { get; set; }

        public virtual User Sender { get; set; }
        public virtual User Receiver { get; set; }

        public string Content { get; set; }

        public string OriginalCultureInfoEnglishName { get; set; }
        public string ForeignCultureInfoEnglishName { get; set; }
    }

public class Language
    {
        [Key]
        public int LanguageId { get; set; }
        public string CultureInfoEnglishName { get; set; }
    }

Now i made a Service.svc which has my DatabaseContext so it can directly acces my database models. What i want to achieve is that instead of directly getting the database models i would like to get the DTO models when i query against my service.

A Example of how my dto's would look like

public class UserDTO
    {
        public int UserId { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string UserName { get; set; }
        public string Email { get; set; }
        public string Country { get; set; }
        public string PhoneNumber { get; set; }

        public ICollection<ContactDTO> Contacts { get; set; }

        public virtual LanguageDTO Language { get; set; }

        public UserModel()
        {
            Contacts = new List<ContactDTO>();
        }
    }

public class ContactDTO
    {
        public int UserId { get; set; }

        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string UserName { get; set; }
        public string Email { get; set; }

        public string Country { get; set; }
        public string PhoneNumber { get; set; }

        public virtual LanguageDTO Language { get; set; }
    }

public class LanguageDTO
    {
        public int LanguageId { get; set; }
        public string CultureInfoEnglishName { get; set; }
    }

public class MessageDTO
    {
        public int MessageId { get; set; }
        public DateTime SentDate { get; set; }

        public virtual ContactDTO Sender { get; set; }
        public virtual ContactDTO Receiver { get; set; }

        public string Content { get; set; }

        public string OriginalCultureInfoEnglishName { get; set; }
        public string ForeignCultureInfoEnglishName { get; set; }
    }

Now is it possible to do it like this by making a different context that i can use in my service.svc or is there any other way to achieve the this?

for example i would like to get ContactDto by userid which is a user but with less properties because they are not relevant in the client application. I see this happening by a uri http://localhost:54895/Service.svc/ContactDto(1)

Hopefully anyone can clear this up for me because it is really frustrating :)

Answer 1

I'm not sure that what you're interested in is possible, exactly. You are looking to have multiple entity sets per type (aka MEST ), and I don't know how well that's supported.

Beyond that point, and into a discussion around DTOs in general...

If you use custom providers, you can implement your own IDataServiceMetadataProvider and IDataServiceQueryProvider . When your service starts, you can make calls into the IDataServiceMetadataProvider to control what entities and properties are exposed or hidden -- including exposing properties that do not actually exist on your entity. The upshot is that you end up with a DTO without coding a DTO class. The exposed metadata is the DTO. This is a good resource for creating your own providers.

In your case, this isn't a 100% solution, because you can't selectively choose when a property is exposed and when it's not.

Hope this helps...