public OverrideEvaluatorEntry(OverrideEvaluator evaluator, int layer)
 {
     this.evaluator = evaluator;
     this.layer     = layer;
 }
 /// <summary>
 /// Adds an override evaluator on the specified layer.
 /// </summary>
 /// <param name="evaluator"></param>
 public void AddOverrideEvaluator(OverrideEvaluator evaluator, int layer)
 {
     this.layers.Add(new OverrideEvaluatorEntry(evaluator, layer));
     this._layerSortDirty = true;
 }