Public Overloads Function Encrypt( _
   ByVal text As String _
) As String

public string Encrypt( 
   string text
)

byte[] ivrandom = new byte[16];
new Random().NextBytes(ivrandom);

using (AESCryptoKey k1 = new AESCryptoKey())
using (AESCryptoKey k2 = new AESCryptoKey(k1.Key, k1.IV))
using (AESCryptoKey kBadIv = new AESCryptoKey(k1.Key, ivrandom))
{
    Assert.AreEqual(k1.Key, k2.Key);
    Assert.AreEqual(k1.IV, k2.IV);
    Assert.AreEqual("test", k2.Decrypt(k1.Encrypt("test")));

    Assert.AreEqual(k1.Key, kBadIv.Key);
    Assert.AreNotEqual(k1.IV, kBadIv.IV);
    try
    {   //one of two possible outcomes, junk or exception
        Assert.AreNotEqual("test", kBadIv.Decrypt(k1.Encrypt("test")));
    }
    catch (System.Security.Cryptography.CryptographicException) { }
}

Dim ivrandom As Byte() = New Byte(16) {}
New Random().NextBytes(ivrandom)

Using k1 As New AESCryptoKey()
    Using k2 As New AESCryptoKey(k1.Key, k1.IV)
        Using kBadIv As New AESCryptoKey(k1.Key, ivrandom)
            Assert.AreEqual(k1.Key, k2.Key)
            Assert.AreEqual(k1.IV, k2.IV)
            Assert.AreEqual("test", k2.Decrypt(k1.Encrypt("test")))

            Assert.AreEqual(k1.Key, kBadIv.Key)
            Assert.AreNotEqual(k1.IV, kBadIv.IV)
            Try
                'one of two possible outcomes, junk or exception
                Assert.AreNotEqual("test", kBadIv.Decrypt(k1.Encrypt("test")))
            Catch generatedExceptionName As System.Security.Cryptography.CryptographicException
            End Try
        End Using
    End Using
End Using