Question

I have a new question for WCF gurus.

So, I have a class User which is close to the ‘User’ representation from the DB which I use for database operations. Now, I would like to have 2 different service contracts that use this class as data contract, but each in their own way… I mean,

public class DBLayer
{
    void InsertUsers(List<User> userList)
    {
        // both 'PropertyVisibleForService1' and 'PropertyVisibleForService2'
        // are used HERE to be inserted into their columns 
    }
}

[DataContract]
public class User
{
  [DataMember] public string PropertyVisibleOnlyForService1{...}
  [DataMember] public string PropertyVisibleOnlyForService2{...}
}

[ServiceContract]
public interface IService1  
{   
   List<User> GetUsers();  // user with 'PropertyVisibleOnlyForService1' inside
}

[ServiceContract]
public interface IService2  
{   
    List<User> GetUsers(); // user with 'PropertyVisibleOnlyForService2' inside 
}

So, the idea is that each service will get a different kind of user, subset of 'User'. Keeping in mind that I want to use the 'User' as is for DB operations, what would be my options to achieve this? Do I really need to create different data contracts or is there another smarter way?

Best would be to not only give me the solution, but also to explain me some best practices and alternatives.

Thank you in advance.

EDIT1:
I added a dummy DBLayer class here for a better overview and why I think the inheritance may not be good in this case.

A solution would be of having another ‘UserForService1‘ and ‘UserForService2‘ as data contracts which would map at the end from/into an ‘User‘ but I wanted some other points of view.

EDIT2: Very good article which helped me in this case: http://bloggingabout.net/blogs/vagif/archive/2009/03/29/iextensibledataobject-is-not-only-for-backward-compatibility.aspx

Answer 1

You could create separate DTO’s for each service but your case would actually be ideal for a Decorator pattern:

[DataContract]
public class UserForService1 : User
{
     private User mUser;
     public UserForService1(User u)
     {
         mUser = u;
     }

     //expose only properties you'd like the user of this data contract to see
     [DataMember]
     public string SomeProperty
     {
         get
         {
            //always call into the 'wrapped' object
            return mUser.SomeProperty;
         }
         set
         {
            mUser.SomeProperty = value;
         }
     }
     // etc...
}

and for Service2 similar code, that exposes only what you care for there…