Winform chart 画曲线时报错：ThrowInvalidOperationException

  HResult=0x80131509
  Message=集合已修改；可能无法执行枚举操作。
  Source=mscorlib
  StackTrace:
   在 System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   在 System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   在 System.Collections.Generic.List`1.Enumerator.MoveNext()
   在 System.Windows.Forms.DataVisualization.Charting.ChartPicture.IsToolTipsEnabled()
   在 System.Windows.Forms.DataVisualization.Charting.ChartPicture.Paint(Graphics graph, Boolean paintTopLevelElementOnly)
   在 System.Windows.Forms.DataVisualization.Charting.Chart.OnPaint(PaintEventArgs e)
   在 System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)
   在 System.Windows.Forms.Control.WmPaint(Message& m)
   在 System.Windows.Forms.Control.WndProc(Message& m)
   在 System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   在 System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   在 System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)