What's the best way to clean up a URL with a title in it?

It is generally best to go with the regular whitelist expression approach instead of removing all unwanted characters, because you will definitely miss out on some of them.

The answers here are fine, but I personally didn't want to completely remove the umlauts and accented characters. So the final solution I came up with looks like this:

public static string CleanUrl(string value)
{
    if (value.IsNullOrEmpty())
        return value;

    // replace hyphens to spaces, remove all leading and trailing whitespace
    value = value.Replace("-", " ").Trim().ToLower();

    // replace multiple whitespace to one hyphen
    value = Regex.Replace(value, @"[\s]+", "-");

    // replace umlauts and eszett with their equivalent
    value = value.Replace("ß", "ss");
    value = value.Replace("ä", "ae");
    value = value.Replace("ö", "oe");
    value = value.Replace("ü", "ue");

    // removes diacritic marks (often called accent marks) from characters
    value = RemoveDiacritics(value);

    // remove all left unwanted chars (white list)
    value = Regex.Replace(value, @"[^a-z0-9\s-]", String.Empty);

    return value;
}

      

        
        
        
      

    

The method used is RemoveDiacritics

based on the answer from Blair Conrad :

public static string RemoveDiacritics(string value)
{
    if (value.IsNullOrEmpty())
        return value;

    string normalized = value.Normalize(NormalizationForm.FormD);
    StringBuilder sb = new StringBuilder();

    foreach (char c in normalized)
    {
        if (CharUnicodeInfo.GetUnicodeCategory(c) != UnicodeCategory.NonSpacingMark)
            sb.Append(c);
    }

    Encoding nonunicode = Encoding.GetEncoding(850);
    Encoding unicode = Encoding.Unicode;

    byte[] nonunicodeBytes = Encoding.Convert(unicode, nonunicode, unicode.GetBytes(sb.ToString()));
    char[] nonunicodeChars = new char[nonunicode.GetCharCount(nonunicodeBytes, 0, nonunicodeBytes.Length)];
    nonunicode.GetChars(nonunicodeBytes, 0, nonunicodeBytes.Length, nonunicodeChars, 0);

    return new string(nonunicodeChars);
}

      

        
        
        
      

    

Hope this helps someone to challenge it by adding urls and storing umlauts and friends at the same time with their url equivalent.