ConfigurationManager.AppSettings - How to modify and save?

Question

It might sound too trival to ask and I do the same thing as suggested in articles, yet it doesn\'t work as expected. Hope someone can point me to the right direction.

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Answer 1

Remember that ConfigurationManager uses only one app.config - one that is in startup project.

If you put some app.config to a solution A and make a reference to it from another solution B then if you run B, app.config from A will be ignored.

So for example unit test project should have their own app.config.

Answer 2

You can change it manually:

private void UpdateConfigFile(string appConfigPath, string key, string value)
{
     var appConfigContent = File.ReadAllText(appConfigPath);
     var searchedString = $"<add key=\"{key}\" value=\"";
     var index = appConfigContent.IndexOf(searchedString) + searchedString.Length;
     var currentValue = appConfigContent.Substring(index, appConfigContent.IndexOf("\"", index) - index);
     var newContent = appConfigContent.Replace($"{searchedString}{currentValue}\"", $"{searchedString}{newValue}\"");
     File.WriteAllText(appConfigPath, newContent);
}

Answer 3

Try adding this after your save call.

ConfigurationManager.RefreshSection( "appSettings" );