<PackageReference Include="System.Configuration.ConfigurationManager" Version="7.0.0-preview.4.22229.4" />

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.
SettingsPropertyValue GetPreviousVersion(SettingsContext context, SettingsProperty property)

Retrieves the previous value of a given SettingsProperty. This is used in conjunction with Upgrade.

void Reset(SettingsContext context)

Resets all settings to their "default" values.

void Upgrade(SettingsContext context, SettingsPropertyCollection properties)

Indicates to the provider that the app has been upgraded. This is a chance for the provider to upgrade its stored settings as appropriate.