namespace System.ServiceModel.Channels { public interface IDuplexSession : IInputSession, ISession, IOutputSession { IAsyncResult BeginCloseOutputSession(AsyncCallback callback, object state); IAsyncResult BeginCloseOutputSession(TimeSpan timeout, AsyncCallback callback, object state); void CloseOutputSession(); void CloseOutputSession(TimeSpan timeout); void EndCloseOutputSession(IAsyncResult result); } }