<PackageReference Include="System.Configuration.ConfigurationManager" Version="10.0.0-preview.7.25380.108" />

System.Configuration.ConfigurationPropertyAttribute

Declaratively instructs .NET to instantiate a configuration property. This class cannot be inherited.
namespace System.Configuration { public sealed class ConfigurationPropertyAttribute : Attribute { public string Name { get; } public object DefaultValue { get; set; } public ConfigurationPropertyOptions Options { get; set; } public bool IsDefaultCollection { get; set; } public bool IsRequired { get; set; } public bool IsKey { get; set; } public ConfigurationPropertyAttribute(string name); } }