调用DLL实现字符的加密与解密，其中dll中有自己定义的加密和解密方法，在c#中调用这两个方法，即可实现字符串的加密与解密。(Call DLL to achieve the characters of encryption and decryption, in which DLL has its own definition of encryption and decryption methods, call these two methods in c#, you can achieve th