Edit Config - Replace Key Value

Config.cs

private void SaveConfig(string key, string value)
{
    var config = ConfigurationManager.OpenExeConfiguration(Path.Combine(AssemblyDirectory, Assembly.GetExecutingAssembly().ManifestModule.Name));
    var applicationSectionGroup = config.GetSectionGroup("applicationSettings");
    var applicationConfigSection = applicationSectionGroup.Sections["AsyncLogging.Properties.Settings"];
    var clientSection = (ClientSettingsSection)applicationConfigSection;

    var applicationSetting = clientSection.Settings.Get(key);
    
    applicationSetting.Value.ValueXml.InnerText = value;    
    
    applicationConfigSection.SectionInformation.ForceSave = true;

    config.Save();

    config.Save(ConfigurationSaveMode.Modified);
    ConfigurationManager.RefreshSection("applicationSettings/AsyncLogging.Properties.Settings");
    ConfigurationManager.RefreshSection("AppSettings");
}