public static string encode(string text)
{
    byte[] mybyte = System.Text.Encoding.UTF8.GetBytes(text);
    string returntext = System.Convert.ToBase64String(mybyte);
    return returntext;
}

public static string decode(string text)
{
    byte[] mybyte = System.Convert.FromBase64String(text);
    string returntext = System.Text.Encoding.UTF8.GetString(mybyte);
    return returntext;
}