<PackageReference Include="System.Configuration.ConfigurationManager" Version="8.0.0-preview.1.23110.8" />

ConfigurationCollectionAttribute

Used on classes derived from ConfigurationElementCollection. Specifies the collection item type and verbs used for add/remove/clear.
public string AddItemName { get; set; }

public string ClearItemsName { get; set; }

public Type ItemType { get; }

public string RemoveItemName { get; set; }