/// <summary>
 ///
 /// </summary>
 /// <param name="eval"></param>
 /// <returns>Cached wrapper</returns>
 public static EvaluationWrapper Wrap(this Evaluation eval)
 {
     if (wrapper == null)
     {
         wrapper = new EvaluationWrapper(eval);
     }
     return(wrapper);
 }
 /// <summary>
 /// 
 /// </summary>
 /// <param name="eval"></param>
 /// <returns>Cached wrapper</returns>
 public static EvaluationWrapper Wrap(this Evaluation eval)
 {
     if (wrapper == null) wrapper = new EvaluationWrapper(eval);       
     return wrapper;
 }