/// <summary>
 /// The repository defaults to using "id" as the parameter to look for in the ref url of an annotation.
 /// </summary>
 private void SetPrimaryRefParameter(string primaryRefParameter, IProgress progress)
 {
     if (_indexOfAllAnnotationsByKey != null)
     {
         _observers.Remove(_indexOfAllAnnotationsByKey);
     }
     if (!string.IsNullOrEmpty(primaryRefParameter))
     {
         _indexOfAllAnnotationsByKey = new IndexOfAllAnnotationsByKey(primaryRefParameter);
         AddObserver(_indexOfAllAnnotationsByKey, progress);
     }
 }
 /// <summary>
 /// The repository defaults to using "id" as the parameter to look for in the ref url of an annotation.
 /// </summary>
 private void SetPrimaryRefParameter(string primaryRefParameter, IProgress progress)
 {
     if (_indexOfAllAnnotationsByKey != null)
     {
         _observers.Remove(_indexOfAllAnnotationsByKey);
     }
     if(!string.IsNullOrEmpty(primaryRefParameter))
     {
         _indexOfAllAnnotationsByKey = new IndexOfAllAnnotationsByKey(primaryRefParameter);
         AddObserver(_indexOfAllAnnotationsByKey, progress);
     }
 }