public void StartUserStream()
{
var newStream = new TwitterUserstream(this.Api);
newStream.StatusArrived += userStream_StatusArrived;
newStream.Started += userStream_Started;
newStream.Stopped += userStream_Stopped;
newStream.Start(this.AllAtReply, this.TrackWord);
var oldStream = Interlocked.Exchange(ref this.userStream, newStream);
oldStream?.Dispose();
}