How to modify my App.exe.config keys at runtime?

Question

In my app.config I have this section

<appSettings>     <add key ="UserId" value ="myUserId"/>      // several other <add key>s </appSettings> 

Usually I access the values using userId = ConfigurationManager.AppSettings["UserId"]

If I modify it using ConfigurationManager.AppSettings["UserId"]=something, the value is not saved to the file, and next time I load the application, it uses the old value.

How can I change the value of some app.config keys during runtime?

Answer 1

System.Configuration.Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);  config.AppSettings.Settings["UserId"].Value = "myUserId";      config.Save(ConfigurationSaveMode.Modified); 

You can read about ConfigurationManager here

Answer 2

On a side note.

If something in your app.config needs to change at runtime...its possible there's a better place to keep that variable.

App.config is used for constants. At worst case something with a one time initialization.