public class Settings
{
    public Settings()
    {
        SomeString = Helpers.GetSetting("SomeString", "DefaultString");
        SomeInt = Helpers.GetSetting("SomeInt", 9, int.TryParse);
        SomeTimeSpan = Helpers.GetSetting("SomeTimeSpan", new TimeSpan(60), Helpers.TimeSpanParser);
    }

    public string SomeString { get; set; }

    public int SomeInt { get; set; }

    public TimeSpan SomeTimeSpan { get; set; }
}

public static class Helpers
{
    public static T GetSetting<T>(string appSetting, T @default, TryParseHandler<T> handler) where T : struct
    {
        var value = ConfigurationManager.AppSettings[appSetting];

        if (string.IsNullOrEmpty(value))
        {
            return @default;
        }

        T result;

        if (handler(value, out result))
        {
            return result;
        }

        throw new Exception(); // Swap to something better :)
    }

    public static string GetSetting(string appSetting, string @default)
    {
        return ConfigurationManager.AppSettings[appSetting];
    }

    public static bool TimeSpanParser(string value, out TimeSpan result)
    {
        result = TimeSpan.FromSeconds(double.Parse(value));
        return true;
    }

    public delegate bool TryParseHandler<T>(string value, out T result);
}