CombiningSettingsReader

gistfile1.txt

public class CombiningSettingsReader : ISettingsReader
    {
        private readonly ISettingsReader[] _settingsReaders;

        public CombiningSettingsReader(params ISettingsReader[] settingsReaders)
        {
            _settingsReaders = settingsReaders;
        }

        public string ReadValue(string key)
        {
            return _settingsReaders.Select(r => r.ReadValue(key)).FirstOrDefault(v => v != null);
        }

        public IEnumerable<string> AllKeys
        {
            get { return _settingsReaders.SelectMany(r => r.AllKeys).Distinct(); }
        }
    }

    public class ConnectionStringsSettingsReader : ISettingsReader
    {
        private readonly Lazy<Dictionary<string, string>> _settings;

        public ConnectionStringsSettingsReader()
        {
            _settings = new Lazy<Dictionary<string, string>>(ReadSettingsFromConfigFile);
        }

        public string ReadValue(string key)
        {
            string value;
            _settings.Value.TryGetValue(key, out value);
            return value;
        }

        public IEnumerable<string> AllKeys
        {
            get { return _settings.Value.Keys; }
        }

        private Dictionary<string, string> ReadSettingsFromConfigFile()
        {
            return ConfigurationManager.ConnectionStrings.OfType<ConnectionStringSettings>()
                .ToDictionary(k => k.Name, k => k.ConnectionString);
        }