Rijndael 256 encryption: Java and .NET do not match
Your results are the same, as far as I can see - it's just that in Java, bytes are signed. (That's icky, but it doesn't affect the actual bits you're getting.)
If you add 256 to every negative value in the Java results, you'll see they're the same as the .NET code:
.NET: 241 100 194 184 166Java: -15 100 -62 -72 -90Java+256: 241 100 194 184 166for -ve(etc)
Alternatively, just print out the unsigned hex representation of the two byte arrays - or even base64-encode them - and you'll see they're the same.