System.Uri.GetCombinedString C# (CSharp) Method

        private unsafe static ParsingError GetCombinedString(Uri baseUri, string relativeStr,
            bool dontEscape, ref string result)
        {
            // NB: This is not RFC2396 compliant although it is inline with w3c.org recommendations
            // This parser will allow the relativeStr to be an absolute Uri with the different scheme
            // In fact this is strict violation of RFC2396
            //
            for (int i = 0; i < relativeStr.Length; ++i)
            {
                if (relativeStr[i] == '/' || relativeStr[i] == '\\' || relativeStr[i] == '?' || relativeStr[i] == '#')
                {
                    break;
                }
                else if (relativeStr[i] == ':')
                {
                    if (i < 2)
                    {
                        // Note we don't support one-letter Uri schemes.
                        // Hence anything like x:sdsd is a relative path and be added to the baseUri Path
                        break;
                    }
                    fixed (char* sptr = relativeStr) // relativeStr.Substring(0, i) represents the scheme
                    {
                        UriParser syntax = null;
                        if (CheckSchemeSyntax(sptr, (ushort)i, ref syntax) == ParsingError.None)
                        {
                            if (baseUri.Syntax == syntax)
                            {
                                //Remove the scheme for backward Uri parsers compatibility
                                if (i + 1 < relativeStr.Length)
                                {
                                    relativeStr = relativeStr.Substring(i + 1);
                                }
                                else
                                {
                                    relativeStr = string.Empty;
                                }
                            }
                            else
                            {
                                // This is the place where we switch the scheme.
                                // Return relative part as the result Uri.
                                result = relativeStr;
                                return ParsingError.None;
                            }
                        }
                    }
                    break;
                }
            }

            if (relativeStr.Length == 0)
            {
                result = baseUri.OriginalString;
                return ParsingError.None;
            }

            result = CombineUri(baseUri, relativeStr, dontEscape ? UriFormat.UriEscaped : UriFormat.SafeUnescaped);
            return ParsingError.None;
        }