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

        internal static string Escape(string input)
        {
            for (int i = 0; i < input.Length; i++)
            {
                if (IsMetachar(input[i]))
                {
                    StringBuilder sb = StringBuilderCache.Acquire();
                    char ch = input[i];
                    int lastpos;

                    sb.Append(input, 0, i);
                    do
                    {
                        sb.Append('\\');
                        switch (ch)
                        {
                            case '\n':
                                ch = 'n';
                                break;
                            case '\r':
                                ch = 'r';
                                break;
                            case '\t':
                                ch = 't';
                                break;
                            case '\f':
                                ch = 'f';
                                break;
                        }
                        sb.Append(ch);
                        i++;
                        lastpos = i;

                        while (i < input.Length)
                        {
                            ch = input[i];
                            if (IsMetachar(ch))
                                break;

                            i++;
                        }

                        sb.Append(input, lastpos, i - lastpos);
                    } while (i < input.Length);

                    return StringBuilderCache.GetStringAndRelease(sb);
                }
            }

            return input;
        }