An operation contract is defined within a service contract. It defines the parameters and return type of an operation. An operation contract can also defines operation-level settings, like as the transaction flow of the operation, the directions of the operation (one-way, two-way, or both ways), and fault contract of the operation.
[ServiceContract]
interface IMyContract {
[FaultContract(typeof(MyFaultContract))]
[OperationContract]
string MyMethod();
}