Microsoft.Extensions.Configuration.Abstractions by Microsoft

<PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="3.1.22" />

 IConfiguration

public interface IConfiguration
Represents a set of key/value application configuration properties.
string this[string key] { get; set; }

Gets or sets a configuration value.

Gets the immediate descendant configuration sub-sections.

Returns a IChangeToken that can be used to observe when this configuration is reloaded.

Gets a configuration sub-section with the specified key.