System.Uri.CreateHostStringHelper C# (CSharp) Method

        private static string CreateHostStringHelper(string str, ushort idx, ushort end, ref Flags flags, ref string scopeId)
        {
            bool loopback = false;
            string host;
            switch (flags & Flags.HostTypeMask)
            {
                case Flags.DnsHostType:
                    host = DomainNameHelper.ParseCanonicalName(str, idx, end, ref loopback);
                    break;

                case Flags.IPv6HostType:
                    // The helper will return [...] string that is not suited for Dns.Resolve()
                    host = IPv6AddressHelper.ParseCanonicalName(str, idx, ref loopback, ref scopeId);
                    break;

                case Flags.IPv4HostType:
                    host = IPv4AddressHelper.ParseCanonicalName(str, idx, end, ref loopback);
                    break;

                case Flags.UncHostType:
                    host = UncNameHelper.ParseCanonicalName(str, idx, end, ref loopback);
                    break;

                case Flags.BasicHostType:
                    if (StaticInFact(flags, Flags.DosPath))
                    {
                        host = string.Empty;
                    }
                    else
                    {
                        // This is for a registry-based authority, not relevant for known schemes
                        host = str.Substring(idx, end - idx);
                    }
                    // A empty host would count for a loopback
                    if (host.Length == 0)
                    {
                        loopback = true;
                    }
                    //there will be no port
                    break;

                case Flags.UnknownHostType:
                    //means the host is *not expected* for this uri type
                    host = string.Empty;
                    break;

                default:
                    throw GetException(ParsingError.BadHostName);
            }

            if (loopback)
            {
                flags |= Flags.LoopbackHost;
            }
            return host;
        }