ideas for message passing

listener.cs

public enum HostMessageEnum 
{
   SendRequestHeader,
   SendRequestHeadersComplete,
   SendRequestBodyStart,
   SendRequestBodyPart,
   SendRequestBodyComplete,
   BeginGetResponse,
   Error
}

public enum AppMessageEnum
{ 
   SendResponseHeader,
   SendResponseHeadersComplete,
   SendResponseStatus,
   SendResponseBodyStart,
   SendResponseBodyPart,
   SendResponseBodyComplete,
   Error
}

public class Host
{
   public Func<HostMessageEnum op, object data, bool received> SendMessageToApp;

   public Host() {
      //Register Listen function delegate here
      SendMessageToApp = new App(Listen).Create() /* Listen is a delegate for Listen below */;
    }
   
   public bool Listen(AppMessageEnum op, object data)
   {
      switch(op) {
          case SendResponseHeader: 
              var header = data as KeyValuePair<string,string>;
              if(header == null) {
                 SendMessagetoApp(HostMessageEnum.Error, 
                                  new Exception("data in message did not conform to this operation"));
                 return false;
              }
              //spin out another thread here that writes headers to the socket
              //passing SendMessageToApp around
              return true;
      }
   }
}

public class App
{
   public Func<AppMessageEnum op, object data, bool received> SendMessageToHost;

   public App(Action<AppMessageEnum op, object data> delegate) {
      SendMessageToHost = delegate;
   }

   public Func<HostMessageEnum op, object data, bool received> Create() {
      return Listen //delegate for Listen below
   }
   
   public bool Listen(HostMessageEnum op, object data)
   {
      switch(op) {
          case BeginGetResponse:
              //spin out another thread that sends headers 
              //host and body parts to the host message passing 
              //SendMessageToHost around
              return true;
      }
   }
}