internal void Init()
 {
     this.DetachEvents();
     this.groups    = null;
     this.sheet     = null;
     this.evaluator = null;
 }
 public WorksheetSparklineGroupManager(ISparklineSheet sheet, ICalcEvaluator calcEvaluator)
 {
     this.Init();
     this.Sheet         = sheet;
     this.CalcEvaluator = calcEvaluator;
 }