Helper class to generate a slug

FriendlyUrlHelper.cs

// Totally ripped from how Stackoverflow does it: https://stackoverflow.com/questions/25259/how-does-stack-overflow-generate-its-seo-friendly-urls/25486
public static class FriendlyUrlHelper
{
  public static string GetFriendlyTitle(string title, bool remapToAscii = false, int maxlength = 80)
  {
    if (title == null)
    {
      return string.Empty;
    }

    int length = title.Length;
    bool prevdash = false;
    StringBuilder stringBuilder = new StringBuilder(length);
    char c;

    for (int i = 0; i < length; ++i)
    {
      c = title[i];
      if ((c >= 'a' && c <= 'z') || (c >= '0' && c <= '9'))
      {
        stringBuilder.Append(c);
        prevdash = false;
      }
      else if (c >= 'A' && c <= 'Z')
      {
        // tricky way to convert to lower-case
        stringBuilder.Append((char)(c | 32));
        prevdash = false;
      }
      else if ((c == ' ') || (c == ',') || (c == '.') || (c == '/') ||
        (c == '\\') || (c == '-') || (c == '_') || (c == '='))
      {
        if (!prevdash && (stringBuilder.Length > 0))
        {
          stringBuilder.Append('-');
          prevdash = true;
        }
      }
      else if (c >= 128)
      {
        int previousLength = stringBuilder.Length;

        if (remapToAscii)
        {
          stringBuilder.Append(RemapInternationalCharToAscii(c));
        }
        else
        {
          stringBuilder.Append(c);
        }

        if (previousLength != stringBuilder.Length)
        {
          prevdash = false;
        }
      }

      if (i == maxlength)
      {
        break;
      }
    }

    if (prevdash)
    {
      return stringBuilder.ToString().Substring(0, stringBuilder.Length - 1);
    }
    else
    {
      return stringBuilder.ToString();
    }
  }

  /// <summary>
  /// Remaps the international character to their equivalent ASCII characters. See
  /// http://meta.stackexchange.com/questions/7435/non-us-ascii-characters-dropped-from-full-profile-url/7696#7696
  /// </summary>
  /// <param name="character">The character to remap to its ASCII equivalent.</param>
  /// <returns>The remapped character</returns>
  private static string RemapInternationalCharToAscii(char character)
  {
    string s = character.ToString().ToLowerInvariant();
    if ("àåáâäãåąā".Contains(s))
    {
      return "a";
    }
    else if ("èéêëę".Contains(s))
    {
      return "e";
    }
    else if ("ìíîïı".Contains(s))
    {
      return "i";
    }
    else if ("òóôõöøő".Contains(s))
    {
      return "o";
    }
    else if ("ùúûüŭů".Contains(s))
    {
      return "u";
    }
    else if ("çćčĉ".Contains(s))
    {
      return "c";
    }
    else if ("żźž".Contains(s))
    {
      return "z";
    }
    else if ("śşšŝ".Contains(s))
    {
      return "s";
    }
    else if ("ñń".Contains(s))
    {
      return "n";
    }
    else if ("ýÿ".Contains(s))
    {
      return "y";
    }
    else if ("ğĝ".Contains(s))
    {
      return "g";
    }
    else if (character == 'ř')
    {
      return "r";
    }
    else if (character == 'ł')
    {
      return "l";
    }
    else if ("đð".Contains(s))
    {
      return "d";
    }
    else if (character == 'ß')
    {
      return "ss";
    }
    else if (character == 'Þ')
    {
      return "th";
    }
    else if (character == 'ĥ')
    {
      return "h";
    }
    else if (character == 'ĵ')
    {
      return "j";
    }
    else
    {
      return string.Empty;
    }
  }
}