说明：  单实例类： 原来从codeproject下载的SingleInstance不能在对话框程序下找到程序上一个运行实例，经我修改后能正确用于对话框程序。--pclion
(Single-instance categories: the original download from codeproject the SingleInstance procedures should not be found in the dialog box procedure on a running instance, the right to my revised procedures for the dialog box.- pclion)