How to get a reference to IDuplexChannel, IDuplexSessionChannel or IOutputChannel in Wcf

I have a duplex Wcf service and I'd like to get a reference to IDuplexChannel, IDuplexSessionChannel or IOutputChannel so that I can use the non-blocking BeginSend method.

On my server, inside of the handler for the initiating method I have the following (I have tried every interface that I listed in place of IOutputChannel. None of them seem to exist.)

_clientCb = OperationContext.Current.GetCallbackChannel<IDxClientCb>();
_channel = OperationContext.Current.Channel;
_duplexChannel = _channel as IOutputChannel;
Debug.Print("Service IOutputCha开发者_开发百科nnel null: {0}", _duplexChannel == null);

Similarly, in the client I have tried to cast the return value of DuplexChannelFactory.CreateChannel() to any of these interfaces and I always get back a null.

How do I get a reference to one of these?

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Why do you want to do that? If you want to do async operations, just declare your callback contract with async operations and use those instead? (see http://msdn.microsoft.com/en-us/library/ms734701.aspx)