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

System.Configuration.RegexStringValidatorAttribute

Declaratively instructs .NET to perform string validation on a configuration property using a regular expression. This class cannot be inherited.
namespace System.Configuration { public sealed class RegexStringValidatorAttribute : ConfigurationValidatorAttribute { public string Regex { get; } public RegexStringValidatorAttribute(string regex); } }