<PackageReference Include="System.Configuration.ConfigurationManager" Version="10.0.1" />

System.Configuration.ConfigurationSettings

public sealed class ConfigurationSettings
Provides runtime versions 1.0 and 1.1 support for reading configuration sections and common configuration settings.
public static NameValueCollection AppSettings { get; }

Gets a read-only collection of the application settings from the configuration file.

public static object GetConfig(string sectionName)

Returns the ConfigurationSection object for the passed configuration section name and path.