I have a Web Site which takes userId and encrypts it with RijndaelManaged provider.
After it encrypts this data, it will put into a queue. As my understanding every data should be encrypted with different IV value and this can be public.
To decrypt data that was encrypted using one of the SymmetricAlgorithm classes, you must set the Key property and the IV property to the same values that were used for encryption. For a symmetric algorithm to be useful, the secret key must be known only to the sender and the receiver.
Additionally there is a Windows Service reads from this queue and tries to decrypt data. But since every value in the queue is encrypted with different IV, how would Windows Service know which IV to use?
Should I store it along side with encrypted data like;
MRibePnbXiN578TUAZcITw== - MyIVValueIsHere
Or is there a known approach needs to be taken?
Yes that is exactly what you should do if you use AES-CBC. You should generate the IV randomly for each message (with a cryptographically secure random generator such as RNGCryptoServiceProvider). Then send the IV along with the encrypted message.
Consider also using the AESCryptoServiceProvider, since AES is a standard. AES is the same as Rijndael but with some fixed standardised parameters.