<PackageReference Include="System.Configuration.ConfigurationManager" Version="4.6.0-preview4.19212.13" />

IConfigSystem

public interface IConfigSystem
Defines an interface used by the .NET Framework to support the initialization of configuration properties.
namespace System.Configuration.Internal { public interface IConfigSystem { IInternalConfigHost Host { get; } IInternalConfigRoot Root { get; } void Init(Type typeConfigHost, params object[] hostInitParams); } }