The security validation for this page is invalid. Click Back in your Web browser, refresh the page.............

当要更新记录时出现The security validation for this page is invalid. Click Back in your Web browser, refresh the page, and try your operation again.的错误

设置： site.AllowUnsafeUpdates = true;
          web.AllowUnsafeUpdates = true;

还是没用，解决方案：添加：item.ParentList.ParentWeb.AllowUnsafeUpdates = true;