using System.Text.RegularExpressions;
public static void Main()
var MerchantHost = "intellectmoney.ru";
var arrDomains = new string[] { "intellectcard\\.com", "intellectmoney\\.ru", "localhost" };
string domainsPattern = string.Join("|", arrDomains);
var ownDomainRegex = $@"(\.|^)({domainsPattern})$";
var test = Regex.IsMatch(MerchantHost, ownDomainRegex);