Design the WCF Service without Implementing Interface

using System;
using System.ServiceModel;
using System.ServiceModel.Web;


namespace WCFServiceWithOutUsingInterface
{
    // NOTE: Not implemeting the Inferface and using inferface attribute directly to class
    [ServiceContract ]
    public class Service1 
    {
        [OperationContract]
        public string DisplayName(String value)
        {
            return string.Format("You Name is : {0}", value);
        }

        
    }
}