Encrypt in .Net and decrypt in AS3

I need to encrypt some files in ASP.net and decrypt them in a flash application built with Action Script 3.

AS3 developer found a lib call AS3crypto which seems like a good one for AS3. The idea is encrypt and decrypt using same key. Symmetrical Encryption?

But I am struggling to find .Net equivalent that would use same algorithm for encryption.

I have tried RC4 example from 4guysfromrolla blog which works too slow for me. I have tried AES on this example (http://msdn.microsoft.com/en-us/library/system.security.cryptography.rijndaelmanaged(v=vs.100).aspx) which works great on .Net but I can't seem to decrypt using AS3crypto to get the same file back. AS3crypto doesn't seem to like to have IV for decryption. I can only supply one key.

So far I am lost. How can I encrypt a file in .Net and decrypt it back in AS3 to get the same file back?

Notice: use 16 char length for both Key and IV, ex: Key: 1234567890123456 and IV: 9876543210654321

Here is C# code

    public byte[] Encrypt(byte[] someData, string KEY, string IV)
    {
        //preparing
        byte[] keyBytes = Encoding.UTF8.GetBytes(KEY); 
        byte[] ivBytes = Encoding.UTF8.GetBytes(IV); 


        //here goes encryption
        RijndaelManaged rijndaelManaged = new RijndaelManaged();
        rijndaelManaged.Key = keyBytes;
        rijndaelManaged.IV = ivBytes;
        rijndaelManaged.BlockSize = 128;
        rijndaelManaged.Mode = CipherMode.CBC;
        ICryptoTransform encryptor = rijndaelManaged.CreateEncryptor(rijndaelManaged.Key, rijndaelManaged.IV);

        byte[] result = null;
        using (MemoryStream memoryStream = new MemoryStream())
        {
            using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
            {
                cryptoStream.Write(someData, 0, someData.Length);
                cryptoStream.FlushFinalBlock();
                result = memoryStream.ToArray();
            }
        }

        return result;


    }

And here is AS3 code using AS3Crypto library

    private function decrypt(input:ByteArray, decrKey:String, decrIV:String):ByteArray
    {

        var key:ByteArray = Hex.toArray(Hex.fromString(decrKey));
        var pad:IPad = new NullPad();
        var aes:ICipher = Crypto.getCipher("aes-cbc", key, pad);
        var ivmode:IVMode = aes as IVMode;
        ivmode.IV = Hex.toArray(Hex.fromString(decrIV));
        aes.decrypt(input);

        return input;
    }