在C＃（Winforms）中滚动DataGridView控件的垂直滚动条时观察到的运行时异常

Question

我已经自定义了cellpainting事件处理程序，并尝试向datagridview添加300行，并在滚动垂直滚动条时观察到以下运行时异常。

System.InvalidOperationException: Operation is not valid due to the current state of the object.
   at System.Windows.Forms.DataGridView.ScrollRowsByHeight(Int32 height)
   at System.Windows.Forms.DataGridView.set_VerticalOffset(Int32 value)
   at System.Windows.Forms.DataGridView.DataGridViewVScrolled(Object sender, ScrollEventArgs se)
   at System.Windows.Forms.ScrollBar.OnScroll(ScrollEventArgs se)
   at System.Windows.Forms.ScrollBar.DoScroll(ScrollEventType type)
   at System.Windows.Forms.ScrollBar.WmReflectScroll(Message& m)
   at System.Windows.Forms.ScrollBar.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

此处提供代码：http://pastebin.com/bN5v5PbS