I found two class in C# related to <strong>AES</strong>, and example code of them MSDN provides are similar, what is the difference between these two classes?
System.Security.Cryptography.Aes is an abstract class, representing merely the concept of AES-ness.
AesCng are concrete implementations of AES in managed code, using Windows CAPI, and using Windows CNG (respectively). (On .NET Core that's a lie: AesManaged and AesCryptoServiceProvider both just use a automagic hidden class which uses Windows CNG, macOS Security.framework, or OpenSSL, as available)
If you're unclear on which one you want, you want to create an instance via
Aes.Create() and only use the base type. The only real exception is when using
AesCng with a named key (which is very rare).
AES is the abstract base class while AESManaged is a managed implementation of AES based upon Rijndael symmetric algorithm with a fixed block size and iteration count.