public static void Main (string[] args) {
     String str = "Hello World! 你好,中国!";
     String key = "1234567890";
     String encrypt_data = XXTEA.EncryptToBase64String(str, key);
     Console.WriteLine(encrypt_data);
     Debug.Assert("QncB1C0rHQoZ1eRiPM4dsZtRi9pNrp7sqvX76cFXvrrIHXL6" == encrypt_data);
     String decrypt_data = XXTEA.DecryptBase64StringToString(encrypt_data, key);
     Debug.Assert(str == decrypt_data);
 }