I have an encrypted string from one of our customers.
This string was encrypted using the AES method in Java.
The only thing I have is the key: \"xxxxxxxxxxxxx
Please go through this article "Simple Cryptographer - Simple DES/AES Implementation in C#"
link: http://www.codeproject.com/KB/recipes/Simple_Cryptographer.aspx
Hope this article will help you.
Here are two complete code samples for you:
You might also find c# implementations of AES encryption here on SO interesting.
I found another example Simple encrypting and decrypting data in C# where they use only the Pass Phrase to decrypt.