public override void WriteLine(string message)
 {
     if (_lastMessage == null)
     {
         AddMessageToCollectionOfMessages(new TraceMessageViewModel(message));
     }
     else
     {
         _lastMessage.Message += message;
         _lastMessage          = null;
     }
 }
 void AddMessageToCollectionOfMessages(TraceMessageViewModel message)
 {
     _dispatcher.Invoke(() => Messages.Insert(0, message));
 }