Service Contract

Service contract describes the operation that service provide. A Service can have more than one service contract but it should have at least one Service contract.
Service Contract can be define using [ServiceContract] and [OperationContract] attribute. [ServiceContract] attribute is similar to the [WebServcie] attribute in the WebService and [OpeartionContract] is similar to the [WebMethod] in WebService.

• It describes the client-callable operations (functions) exposed by the service
• It maps the interface and methods of your service to a platform-independent description
• It describes message exchange patterns that the service can have with another party. Some service operations might be one-way; others might require a request-reply pattern
• It is analogous to the element in WSDL

To create a service contract you define an interface with related methods representative of a collection of service operations, and then decorate the interface with the ServiceContract Attribute to indicate it is a service contract. Methods in the interface that should be included in the service contract are decorated with the OperationContract Attribute.

[ServiceContract()]
    public interface ISimpleCalculator
    {
        [OperationContract()]
        int Add(int num1, int num2);
    }

Once we define Service contract in the interface, we can create implement class for this interface.

public  class SimpleCalculator : ISimpleCalculator
    {
    
        public int Add(int num1, int num2)
        {
            return num1 + num2;
        }

    }

With out creating the interface, we can also directly created the service by placing Contract in the implemented class. But it is not good practice of creating the service

[ServiceContract()]
   public class SimpleCalculator 
   {
       [OperationContract()]
       public int Add(int num1, int num2)
       {
           return num1 + num2;
       }

   }

Now you have some fundamental idea on Service contract. Next we will look into Data Contract.