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When you get the error as mentioned in title. Please check the below things: WCF service has to run as administrator If you want to run this service locally then we can workaround this error. For this please follow the below blog: http://blogs.msdn.com/b/avkashchauhan/archive/2011/03/22/opening-an-internal-http-endpoint-with-wcf-servicehost-basichttpbindings-may-cause-system-net-httplistenerexception-system-servicemodel-addressaccessdeniedexception.aspx But the catch here as the blog says, it is totally internal to the machine. External WCF clients cannot communicate with this WCF service. If you are logged in as Local user in the machine. Then run the application in elevated mode to avoid this error.  

Setting Mute/Unmute State on Lync through Lync SDK: UnMute:                            Conversation conv; //Once you have the conversation, set the unmute on Lync as below.   IDictionary < ModalityTypes , Modality > modalities = conv.Modalities; Modality mod = modalities[ ModalityTypes .AudioVideo]; bool canHold = mod.CanInvoke( ModalityAction .Hold); //Check if we can invoke Hold on the conversation. i f (canHold) mod.BeginSetProperty( ModalityProperty .AVModalityAudioCaptureMute, false ,UnMuteOccured, null );     Mute: Mute is simple as mentioned below.   conv.SelfParticipant.BeginSetMute( true ,MuteOccured, null );       private void UnMuteOccured( IAsyncResult ar){} private void MuteOccured( IAsyncResult ar){}