Down Base. Dispose(Boolean) 方法
释放由此控件及其子控件占用的非托管资源，另外还可释放托管资源。Releases the unmanaged resources used by the control and its child controls, and optionally releases the managed resources.
protected: override void Dispose(bool disposing);
protected override void Dispose (bool disposing);
override this.Dispose : bool -> unit
Protected Overrides Sub Dispose (disposing As Boolean)
true to release both managed and unmanaged resources;
false to release only unmanaged resources.