using System;
using System.Linq;
public class Program
{
public static void Main()
var f = new Uri("https://test.whatever.com/hey/yall");
var domain = Uri.TryCreate(f.ToString(), 0, out var uri) ? string.Join('.', uri.Host.Split('.').TakeLast(2)) : null;
Console.WriteLine(domain);
// would actually be
// Domain = Uri.TryCreate(_httpContextAccessor.HttpContext.Request.Headers["Referer"], 0, out var uri) ? string.Join('.', uri.Host.Split('.').TakeLast(2)) : null,
}