public class AppModify

    {

        /// <summary>

        /// 依据连接串名字connectionName返回数据连接字符串

        /// </summary>

        /// <param name="connectionName"></param>

        /// <returns></returns>

        public static string GetConnectionStringsConfig(string connectionName)

        {

            string connectionString =

                    ConfigurationManager.ConnectionStrings[connectionName].ConnectionString.ToString();

            return connectionString;

        }

        /// <summary>

        /// 更新连接字符串

        /// </summary>

        /// <param name="newName"> 连接字符串名称 </param>

        /// <param name="newConString"> 连接字符串内容 </param>

        /// <param name="newProviderName"> 数据提供程序名称 </param>

        public static void UpdateConnectionStringsConfig(string newName,

            string newConString,

            string newProviderName)

        {

            bool isModified = false;    // 记录该连接串是否已经存在

            // 如果要更改的连接串已经存在

            if (ConfigurationManager.ConnectionStrings[newName] != null)

            {

                isModified = true;

            }

            // 新建一个连接字符串实例

            ConnectionStringSettings mySettings =

                new ConnectionStringSettings(newName, newConString, newProviderName);

            // 打开可执行的配置文件*.exe.config

            Configuration config =

                ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

            // 如果连接串已存在，首先删除它

            if (isModified)

            {

                config.ConnectionStrings.ConnectionStrings.Remove(newName);

            }

            // 将新的连接串添加到配置文件中.

            config.ConnectionStrings.ConnectionStrings.Add(mySettings);

            // 保存对配置文件所作的更改

            config.Save(ConfigurationSaveMode.Modified);

            // 强制重新载入配置文件的ConnectionStrings配置节

            ConfigurationManager.RefreshSection("ConnectionStrings");

        }

        public static void UpdateConnectionStringsConfig(string newName,

           string newConString)

        {

            bool isModified = false;    // 记录该连接串是否已经存在

            // 如果要更改的连接串已经存在

            if (ConfigurationManager.ConnectionStrings[newName] != null)

            {

                isModified = true;

            }

            // 新建一个连接字符串实例

            ConnectionStringSettings mySettings =

                new ConnectionStringSettings(newName, newConString);

            // 打开可执行的配置文件*.exe.config

            Configuration config =

                ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

            // 如果连接串已存在，首先删除它

            if (isModified)

            {

                config.ConnectionStrings.ConnectionStrings.Remove(newName);

            }

            // 将新的连接串添加到配置文件中.

            config.ConnectionStrings.ConnectionStrings.Add(mySettings);

            // 保存对配置文件所作的更改

            config.Save(ConfigurationSaveMode.Modified);

            // 强制重新载入配置文件的ConnectionStrings配置节

            ConfigurationManager.RefreshSection("ConnectionStrings");

        }

        /// <summary>

        /// 返回＊.exe.config文件中appSettings配置节的value项

        /// </summary>

        /// <param name="strKey"></param>

        /// <returns></returns>

        public static string GetAppConfig(string strKey)

        {

            foreach (string key in ConfigurationManager.AppSettings)

            {

                if (key == strKey)

                {

                    return ConfigurationManager.AppSettings[strKey];

                }

            }

            return null;

        }

        /// <summary>

        /// 在＊.exe.config文件中appSettings配置节增加一对键、值对

        /// </summary>

        /// <param name="newKey"></param>

        /// <param name="newValue"></param>

        public static void UpdateAppConfig(string newKey, string newValue)

        {

            bool isModified = false;

            foreach (string key in ConfigurationManager.AppSettings)

            {

                if (key == newKey)

                {

                    isModified = true;

                }

            }

            // Open App.Config of executable

            Configuration config =

                ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

            // You need to remove the old settings object before you can replace it

            if (isModified)

            {

                config.AppSettings.Settings.Remove(newKey);

            }

            // Add an Application Setting.

            config.AppSettings.Settings.Add(newKey, newValue);

            // Save the changes in App.config file.

            config.Save(ConfigurationSaveMode.Modified);

            // Force a reload of a changed section.

            ConfigurationManager.RefreshSection("appSettings");

        }

    }