Public Class AESCryptoKey 
   Inherits CryptoKey
   Implements IEncryptDecrypt 

public class AESCryptoKey : CryptoKey, IEncryptDecrypt  

byte[] original = AESCryptoKey.ProcessDefaultIV;
try
{
    Assert.AreEqual(original, new AESCryptoKey().IV);

    byte[] newIv = new byte[16];
    new Random().NextBytes(newIv);
    AESCryptoKey.ProcessDefaultIV = newIv;

    Assert.AreEqual(newIv, AESCryptoKey.ProcessDefaultIV);
    Assert.AreEqual(newIv, new AESCryptoKey().IV);
}
finally
{
    AESCryptoKey.ProcessDefaultIV = original;
}

Dim original As Byte() = AESCryptoKey.ProcessDefaultIV
Try
    Assert.AreEqual(original, New AESCryptoKey().IV)

    Dim newIv As Byte() = New Byte(16) {}
    New Random().NextBytes(newIv)
    AESCryptoKey.ProcessDefaultIV = newIv

    Assert.AreEqual(newIv, AESCryptoKey.ProcessDefaultIV)
    Assert.AreEqual(newIv, New AESCryptoKey().IV)
Finally
    AESCryptoKey.ProcessDefaultIV = original
End Try