如何更新.net中现有配置键的值

以…为例

<add key="IDs" value="001;789;567"/>

如何以编程方式更新(追加)App.config中现有键的值?

<add key="IDs" value="001;789;567;444"/>

我的代码目前有以下添加新键，但我不知道如何更新键。

System.Configuration.Configuration config = System.Configuration.ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.AppSettings.Settings.Add(appKey, appKeyValue);
// Save the changes in App.config file.
config.Save(ConfigurationSaveMode.Modified);

Configuration config = ConfigurationManager.OpenExeConfiguration("YourConfigFilePath");
config.AppSettings.Settings["IDS"].Value = "001;789;567;444";  // Update the value (You could also use your appKey variable rather than the string literal.
config.Save();