<PackageReference Include="System.Configuration.ConfigurationManager" Version="6.0.0-preview.1.21102.12" />

SettingsSerializeAsAttribute

public sealed class SettingsSerializeAsAttribute : Attribute
Specifies the serialization mechanism that the settings provider should use. This class cannot be inherited.
namespace System.Configuration { [AttributeUsage(AttributeTargets.Class | AttributeTargets.Property)] public sealed class SettingsSerializeAsAttribute : Attribute { private readonly SettingsSerializeAs _serializeAs; public SettingsSerializeAs SerializeAs => _serializeAs; public SettingsSerializeAsAttribute(SettingsSerializeAs serializeAs) { _serializeAs = serializeAs; } } }