Not sure if anyone cares anymore since this is so old but I needed to do just that this week and could not find anything on the internet that met my needs. Maybe there is something new in the framework that does this that I was unable find... Regardless, I would post source code but since I wrote it for my company and they tend to frown on that, I'll just outline the approach I took:
Since SslStream takes a stream in the constructor, I implemented my own Stream subtype with an underlying MemoryStream for reads and another for writes. I also pass in the TcpClient to this object as well.
I used the TcpClient to do the handshake for setting up the SSL connection. After authenticating the server or client depending on how I am using it, I then use my two MemoryStreams for the SslStream read/writes.
So for Async writes, I first write my payload to the SslStream which populates my MemoryStream for writing with encrypted data. With the encrypted data from the MemoryStream, I populate the SocketAsyncEventArgs buffer and call the TcpClient SendAsync method. For reads, it's pretty much the opposite.
I can't say it particular excites me to move the data like that but as long as you don't let your MemoryBuffer objects get reallocated constantly, it's not a performance issue. At least this way, I can use just the framework and my own code without relying on third party software.
