<PackageReference Include="System.Configuration.ConfigurationManager" Version="6.0.0" />

IApplicationSettingsProvider

public interface IApplicationSettingsProvider
This interface is an extension to SettingsProvider that a provider can implement to support additional functionality for settings classes that derive from ApplicationSettingsBase.
namespace System.Configuration { public interface IApplicationSettingsProvider { SettingsPropertyValue GetPreviousVersion(SettingsContext context, SettingsProperty property); void Reset(SettingsContext context); void Upgrade(SettingsContext context, SettingsPropertyCollection properties); } }