private char[] TextEncrypt(string content, string secretKey)
{
    char[] data = content.ToCharArray();
    char[] key = secretKey.ToCharArray();

    for (int i = 0; i < data.Length; i++)
    {
        data[i] ^= key[i % key.Length];
    }

    return data;
}

private string TextDecrypt(char[] data, string secretKey)
{
    char[] key = secretKey.ToCharArray();

    for (int i = 0; i < data.Length; i++)
    {
        data[i] ^= key[i % key.Length];
    }

    return new string(data);
}