创建模态对话框实例，这类对话框弹出后，其他程序会被挂起，只有当前对话框响应用户的输入，模态对话框一般要求用户做出某种选择-Create a modeless dialog instance, such pop-up dialog box, the other procedures will be hung, only the current in response to user input dialog box, modal dialog box to make some general re