title: Add variables as prefix to all nLog messages
body: <p>I am using Nlog to log my Ninjatrader Strategies. I want to be able to add the strategy id as prefix to all my nLog messages so that I can filter the entries related to each account on the strategy  separately.</p>
  
  <pre><code> fileTarget.Layout =  "${longdate} ${callsite} ${level} ${event-context:item=MyValue}  ${message}";`
  </code></pre>
  
  <p>My current layout is as above. I tried to use event-context:item but dunno how to print the context item for all messages.</p>
  
  <p>I tried as follows</p>
  
  <pre><code>Logger log = LogManager.GetCurrentClassLogger();
  LogEventInfo theEvent = new LogEventInfo(NLog.LogLevel.Debug, "", this.Account.Name);   
  logger.Log(theEvent);
  </code></pre>
  
  <p>But it ended printing only one line with the context info on the first line Sim101 and not on the other lines.</p>
  
  <pre><code>2012-11-26 15:09:47.9777 NinjaTrader.Strategy.LODHOD.OnStartUp Debug   Sim101
  2012-11-26 15:09:48.3996 NinjaTrader.Strategy.LODHOD.OnBarUpdate Trace   BAR UPDATE
  2012-11-26 15:09:49.7902 NinjaTrader.Strategy.LODHOD.EntryOrders Info   PLACED ENTRY ORDERS
  </code></pre>
  
  <p>How do I print the Sim101 on all the log lines?</p>