UrlSlugGenerator

public static class UrlSlugGenerator
{
    private static readonly IDictionary<string, string> UrlReplacementMap = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
        {
            {"&", "-"},
            {" ", "-"},
            {"/", "-"},
            {"+", "-"},
        };

    private static readonly Regex UrlReplacementRegex = new Regex(string.Format("([{0}])", string.Concat(UrlReplacementMap.Keys.Select(Regex.Escape))), RegexOptions.Compiled);
    private static readonly Regex InvalidCharRegex = new Regex(@"[^\w-]", RegexOptions.Compiled);
    private static readonly Regex MultipleDashesRegex = new Regex("-{2,}", RegexOptions.Compiled);

    public static string Sluggify(string value)
    {
        if (value == null) throw new ArgumentNullException("value");

        var result = UrlReplacementRegex.Replace(value, m => UrlReplacementMap[m.Groups[1].ToString()]);
        result = RemoveDiacritics(result);
        result = InvalidCharRegex.Replace(result, "");
        result = MultipleDashesRegex.Replace(result, "-");
        result = result.Trim('-');
        return result.ToLower();
    }

    private static string RemoveDiacritics(string s)
    {
        var bytes = Encoding.GetEncoding("Cyrillic").GetBytes(s);
        return Encoding.ASCII.GetString(bytes);
    }
}

[TestFixture]
public class UrlSlugGeneratorTests
{
    [TestCase("åäö æł", "aao-al")]
    [TestCase("a - b", "a-b")]
    [TestCase("Força Barça", "forca-barca")]
    [TestCase("ëêéèñûüúùóø", "eeeenuuuuoo")]
    [TestCase("foo ", "foo")]
    [TestCase("a,b;c", "abc")]
    [TestCase("ąćęłńóśźżőűğıİş", "acelnoszzougiis")]
    [TestCase("ăâîşţ", "aaist")]
    [TestCase("ß", "")]
    [TestCase("d.a.d.", "dad")]
    [TestCase("Øyvind", "oyvind")]
    public void Generates_expected_slug(string input, string expected)
    {
        var slug = UrlSlugGenerator.Sluggify(input);
        slug.Should().Be.EqualTo(expected);
    }
}