Dynamic Website Multi-languages Management

using System.Collections.Generic;
using System.Globalization;
using System.IO;

/// <summary>
/// Class to manage language on the website
/// </summary>
public sealed class LanguageManager
{
    public static CultureInfo DefaultCulture = new CultureInfo("en-US");
    private CultureInfo _currentCulture;

    public LanguageManager()
        : this(DefaultCulture)
    {
    }

    public LanguageManager(CultureInfo cultureInfo)
    {
        _currentCulture = cultureInfo;
    }

    public CultureInfo CurrentCulture
    {
        get { return _currentCulture; }
        set { _currentCulture = value; }
    }

    public CultureInfo[] AvailableCultures
    {
        get
        {
            List<CultureInfo> result = new List<CultureInfo>();

            //
            //Only show culture that according resource can be found
            //
            List<string> availableResources = new List<string>();
            string resourcespath = Path.Combine(System.Web.HttpRuntime.AppDomainAppPath, "App_GlobalResources");
            DirectoryInfo dirInfo = new DirectoryInfo(resourcespath);
            foreach (FileInfo fi in dirInfo.GetFiles("lang.*.resx", SearchOption.AllDirectories))
            {
                //Take the cultureName from resx filename, will be smt like en-US
                string cultureName = fi.Name.Replace("lang.", string.Empty).Replace(".resx", string.Empty);
                availableResources.Add(cultureName);
            }

            foreach (CultureInfo culture in CultureInfo.GetCultures(CultureTypes.SpecificCultures))
            {
                //If language file can be found
                if (availableResources.Contains(culture.ToString()))
                {
                    result.Add(culture);
                }
            }

            return result.ToArray();
        }
    }

    public string this[string key]
    {
        get
        {
            string @string = Resources.lang.ResourceManager.GetString(key, _currentCulture);
            //if no value found, get value in default resource
            if (@string == string.Empty) @string = Resources.lang.ResourceManager.GetString(key);

            return (@string != string.Empty) ? @string : key; //if no value found, return key
        }
    }
}