/// <summary>
 /// Returns the value associated to resourceKey inside to the current vocabolary.
 /// </summary>
 /// <param name="resourceKey"></param>
 /// <returns></returns>
 public string this[string resourceKey]
 {
     get
     {
         if (CurrentVocabolary != null)
         {
             if (CurrentVocabolary.ContainsKey(resourceKey) && !string.IsNullOrEmpty(CurrentVocabolary[resourceKey]))
             {
                 return(CurrentVocabolary[resourceKey]);
             }
             ServiceProvider.AddOrUpdateTermAsync(CurrentVocabolary, resourceKey);
         }
         return(null);
     }
 }