Dim aes_CryptoTransform As ICryptoTransform = AesCryptoServiceProvider.Create.CreateEncryptor(aesKeySet.Key, aesKeySet.IV)
Dim textBytes() As Byte = System.Text.Encoding.ASCII.GetBytes(rtb_plaintext.Text)

Dim encrypted() As Byte
using msEncrypt As New MemoryStream()
     using csEncrypt As New CryptoStream(textBytes, aes_CryptoTransform, CryptoStreamMode.write)
          using textStream as New StreamWriter(csEncrypt)
               swEncrypt.Write(plainText)
          End Using
          encrypted = msEncrypt.ToArray()
          csEncrypt.close()
     End Using
End Using

dim textDirectoryPath as String = "C:encryptText.text"
using textFilestream as new Filestream(textDirectoryPath, filemode.create)
     textFilestream.write(encrypted, 0, encrypted.length)
     textFilestream.close()
end using

Dim aes_CryptoTransform As ICryptoTransform = AesCryptoServiceProvider.Create.CreateEncryptor(aesKeySet.Key, aesKeySet.IV)

Dim textBytesToDecrypt() As Byte = File.readAllBytes("C:encryptText.text")
dim plainText as string = nothing

using msEncrypt As New MemoryStream(textBytesToDecrypt)
     using csEncrypt As New CryptoStream(textBytes, aes_CryptoTransform, CryptoStreamMode.read)
          using textStream as New StreamReader(csEncrypt)
              plainText = textStream.readToEnd()
          End Using
          csEncrypt.close()
     End Using
End Using