public static string GetMD5Hash(string text)
{
    var md5 = MD5.Create();
    //another way to create and md5 object is new MD5CryptoServiceProvider();
    return md5.ComputeHash(GetBytes(text)).ToHexString();
}

private static byte[] GetBytes(string text)
{
    return Encoding.UTF8.GetBytes(text);
}