https://learn.microsoft.com/en-us/dotnet/api/system.globalization.cultureandregioninfobuilder.twoletterisoregionname?view=netframework-4.7.2
CultureAndRegionInfoBuilder.TwoLetterISORegionName Property (System.Globalization) | Microsoft Learn
Gets or sets the two-letter code defined in ISO 3166 for the country/region.
property systemglobalizationmicrosoftlearn