System.Text.RegularExpressions.RegexParser.Unescape C# (CSharp) Method

        internal static string Unescape(string input)
        {
            for (int i = 0; i < input.Length; i++)
            {
                if (input[i] == '\\')
                {
                    StringBuilder sb = StringBuilderCache.Acquire();
                    RegexParser p = new RegexParser(CultureInfo.InvariantCulture);
                    int lastpos;
                    p.SetPattern(input);

                    sb.Append(input, 0, i);
                    do
                    {
                        i++;
                        p.Textto(i);
                        if (i < input.Length)
                            sb.Append(p.ScanCharEscape());
                        i = p.Textpos();
                        lastpos = i;
                        while (i < input.Length && input[i] != '\\')
                            i++;
                        sb.Append(input, lastpos, i - lastpos);
                    } while (i < input.Length);

                    return StringBuilderCache.GetStringAndRelease(sb);
                }
            }

            return input;
        }