Contract Inheritance (WCF)

Contract Inheritance

Service contract interfaces can derive from each other, enabling you to define a hierarchy

of contracts. However, the ServiceContract attribute is not inheritable:

[AttributeUsage(Inherited = false,...)]

public sealed class ServiceContractAttribute : Attribute

{…}

 

Consequently, every level in the interface hierarchy must explicitly have the Service Contract attribute.

Service-side contract hierarchy

 

    [ServiceContract]

    interface IUser

    {

        [OperationContract]

        string AddUser(string UserName, string Pass,string email, string firstName, string lastName)

    }

    [ServiceContract]

    interface IAdminUser : IUser

    {

        [OperationContract]

        string DeleteUser(int UserID);

    }

When it comes to implementing a contract hierarchy, a single service class can implement

the entire hierarchy, just as with classic C# programming:

class User : IAdminUser

    {

         public string AddUser(string UserName, string Pass,string email, string firstName, string lastName)

         {

            try

            {

                using (var Context=new MyEntities())

                var user = Context.Users.Where(c => c.UserName == UserName).FirstOrDefault();

                if (user != null)

                    return "Duplicate Username.";

                else

                {

                        Users Us = new Users();

                        Us.UserName = UserName;

                        Us.Password = Pass;

                        Us.Email = email;

                        Us.FirstName = firstName;

                        Us.LastName = lastName;

                        Us.AddedDate = DateTime.Now;

                        Us.Guid = Guid.NewGuid().ToString();

                        Context.AddToUsers(Us);

                        Context.SaveChanges();

                        return Us.UserID.ToString();

                }

            }        

             catch (Exception e)

             {

                return e.Message;

             }

        }

        public string DeleteUser(int UserID)

        {

            try

            {

                using (var Context = new MyEntities())

                {

                    var user = Context.Users.Where(c => c.UserName == UserName).FirstOrDefault();

                    if (user != null)

                       

                        user.IsDeleted = true;

                        Context.SaveChanges();

                        return user.UserName ;

                    }

                }

            }        

             catch (Exception e)

             {

                return e.Message;

             }

 

        }

The host can expose a single endpoint for the bottommost interface in the hierarchy:

<service name = "User">

    <endpoint

    address = "http://localhost:8001/User/"

    binding = "basicHttpBinding"

    contract = "IAdminUser" />

 </service>

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