ASP.NET 修改web.config配置文件

Configuration config = WebConfigurationManager.OpenWebConfiguration("~");//這裏一定要用~，否則會出現‘無法爲請求的配置對象創建一個配置文件’，‘不能使用相對虛擬路徑’等問題
            AppSettingsSection section = (AppSettingsSection)config.GetSection("appSettings");
            string _activityID = ActivityIDTextBox.Text;
            if (section.Settings["ActivityID"] == null)
            {
                section.Settings.Add("ActivityID", _activityID);
            }
            else
            {
                section.Settings["ActivityID"].Value = _activityID;
            }
            config.Save(ConfigurationSaveMode.Modified);