One Way -- Operations

        In One-Way operation mode, client will send a request to the server and does not care whether it is success or failure of service execution. There is no return from the server side, it is one-way communication.

         Client will be blocked only for a moment till it dispatches its call to service. If any exception thrown by service will not reach the server.
 
        Client can continue to execute its statement, after making one-way call to server. There is no need to wait, till server execute. Sometime when one-way calls reach the service, they may not be dispatched all at once but may instead be queued up on the service side to be dispatched one at a time, according to the service's configured concurrency mode behavior.

         If the number of queued messages has exceeded the queue's capacity, the client will be blocked even if it's issued a one-way call. However, once the call is queued, the client will be unblocked and can continue executing, while the service processes the operation in the background.

Definition: 

    One-way operation can be enabled by setting IsOneWay property to true in Operation contract attribute.

[Service Contract]

Public interface IMyService

{

    [Operation Contract (IsOneWay=true)]

    Void MyMethod (EmployeeDetails emp);

}

One-Way Operations and Sessionful Services:

    Let us see the example, what will happen when you use the one-way communication with Sessionful service.

    [Service Contract (SessionMode = SessionMode. Required)]

    Interface IMyContract

    {

        [Operation Contract (IsOneWay = true)]

        Void MyMethod ();

    }

      As per above configuration, when client makes one-way call using MyMethod() operation and if it close the proxy. Client will be blocked until operation completes. It will be good practice, that one-way operation should be applied on per-call and singleton service.

      Suppose If you want to make use of One-way operation in Sessionful service, use in the last operation of the service which will terminate the session. This operation should not return any value.

    [Service Contract (SessionMode = SessionMode. Required)]

      Interface IMyContract

      {

        [Operation Contract]

        void MyMethod1();

        [Operation Contract]

        String MyMethod2 ();

        [Operation Contract (IsOneWay = true, IsInitiating = false,IsTerminating = true)]

        String CloseSessionService (int id);       

    }

One-Way Operations and Exceptions:

       Suppose when we are using BasicHttpBinding or WSHttpBinding, i.e. no transport session is used, if any exception throw by service will not affect the client. Client can make a call to the service using same proxy

[Service Contract]

interface IMyContract

{

   [Operation Contract(IsOneWay = true)]

   void MethodWithError( ); 

   [Operation Contract]

   void MethodWithoutError( );

}

//Client side without transport session

MyContractClient proxy = new MyContractClient( );

proxy.MethodWithError( ); //No exception is thrown from serivce

proxy.MethodWithoutError( ); //Operation will execute properly

proxy.Close( );

In the presence of transport session, any exception thrown by service will fault the client channel. Client will not be able to make new call using same proxy instance.

//Client side transport session

MyContractClient proxy = new MyContractClient( );

proxy.MethodWithError( ); 

proxy.MethodWithoutError( ); //Can not execute because channel is faulted

proxy.Close( );