VB.NET:

Imports System.Security.Cryptography
Imports System.IO
Imports System.TextModule Module1Sub Main()
        Dim inFileName As String = "C:\in.txt"
        Dim outFileName As String = "C:\out.txt"
        Dim password As String = "Joey"
        Dim salt As Byte() = Encoding.Unicode.GetBytes("Salt adds to left spaces")
        Dim key As New Rfc2898DeriveBytes(password, salt)
        Dim rm As New RijndaelManaged()
        rm.Key = key.GetBytes(rm.KeySize / 8)
        rm.IV = key.GetBytes(rm.BlockSize / 8)
        Dim inFile As New FileStream(inFileName, FileMode.Open, FileAccess.Read)
        Dim data(inFile.Length - 1) As Byte
        inFile.Read(data, 0, data.Length)
        Dim encryptor As ICryptoTransform = rm.CreateEncryptor
        Dim outFile As New FileStream(outFileName, FileMode.OpenOrCreate, FileAccess.Write)
        Dim stream As New CryptoStream(outFile, encryptor, CryptoStreamMode.Write)
        stream.Write(data, 0, data.Length)
        stream.Close()
        outFile.Close()
        inFile.Close()
    End SubEnd Module

C#:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;
using System.IO;namespace EncryptingAndDecryptingCS
{
    class Program
    {
        static void Main(string[] args)
        {
            string inFileName = @"C:\in.txt";
            string outFileName = @"C:\out.txt";
            string password = "Joey";
            byte[] salt = Encoding.Unicode.GetBytes("Salt adds to left spaces");
            Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password, salt);
            RijndaelManaged rm = new RijndaelManaged();
            rm.Key = key.GetBytes(rm.KeySize / 8);
            rm.IV = key.GetBytes(rm.BlockSize / 8);
            FileStream inFile = new FileStream(inFileName, FileMode.Open, FileAccess.Read);
            byte[] data = new byte[inFile.Length];
            inFile.Read(data, 0, data.Length);
            ICryptoTransform encryptor = rm.CreateEncryptor();
            FileStream outFile = new FileStream(outFileName, FileMode.OpenOrCreate, FileAccess.Write);
            CryptoStream stream = new CryptoStream(outFile, encryptor, CryptoStreamMode.Write);
            stream.Write(data, 0, data.Length);
            stream.Close();
            outFile.Close();
            inFile.Close();
        }
    }
}