A Windows Communication Foundation (WCF) solution exposes the following contract over an HTTP connection.

[ServiceContract]
public interface IDataService
{
[OperationContract]
string GetData();
}

Existing clients are making blocking calls to GetData. Calls to GetData take five seconds to complete. You need to allow new clients to issue non-blocking calls to get the data, without breaking any existing clients. What should you do?

1. Replace the service interface with the following interface and implement the new methods

   [ServiceContract]
   public intetface IDoSomething
   {
   [OperationContract]
   string DoLongOperation();
   [OperationContract(AsyncPattern= true)]
   IAsyncResult BeginDoLongOperation();
   [OperationContract(AsyncPattern = true)]
   string EndDoLongOperation(lAsyncResult result);
   }

2. Replace the service interface with the following interface and implement the new methods.

   [ServiceContract]
   public interface IDoSomething
   {
   [OperationContract(AsyncPattern=true)]
   IAsyncResult BeginDoLongOperation();
   [OperationContract(AsyncPattern=true)]
   string EndDoLongOperation(IAsyncResult result);
   }

3. Generate a proxy class with asynchronous methods and use it for the new clients.

4. Add a new endpoint to the service that uses a full-duplex binding and use it for the new clients.