form1.cs

File Encrypt classes

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Security.Cryptography;

namespace EncryptFile
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnSelFile_Click(object sender, EventArgs e)
        {
            if (openFile.ShowDialog() == DialogResult.OK)
            {
                txtFilePath.Text = openFile.FileName;
            }
        }

        private void btnEncFile_Click(object sender, EventArgs e)
        {
            // After the user chose where he wants the key file saved
            if (saveKeyFile.ShowDialog() == DialogResult.OK)
            {
                // And after the user chose where he wants the encrypted file saved
                if (saveEncFile.ShowDialog() == DialogResult.OK)
                {
                    FileStream fsFileOut = File.Create(saveEncFile.FileName);
                    // The chryptographic service provider we're going to use
                    TripleDESCryptoServiceProvider cryptAlgorithm = new TripleDESCryptoServiceProvider();
                    // This object links data streams to cryptographic values
                    CryptoStream csEncrypt = new CryptoStream(fsFileOut, cryptAlgorithm.CreateEncryptor(), CryptoStreamMode.Write);
                    // This stream writer will write the new file
                    StreamWriter swEncStream = new StreamWriter(csEncrypt);
                    // This stream reader will read the file to encrypt
                    StreamReader srFile = new StreamReader(txtFilePath.Text);
                    // Loop through the file to encrypt, line by line
                    string currLine = srFile.ReadLine();
                    while (currLine != null)
                    {
                        // Write to the encryption stream
                        swEncStream.Write(currLine);
                        currLine = srFile.ReadLine();
                    }
                    // Wrap things up
                    srFile.Close();
                    swEncStream.Flush();
                    swEncStream.Close();

                    // Create the key file
                    FileStream fsFileKey = File.Create(saveKeyFile.FileName);
                    BinaryWriter bwFile = new BinaryWriter(fsFileKey);
                    bwFile.Write(cryptAlgorithm.Key);
                    bwFile.Write(cryptAlgorithm.IV);
                    bwFile.Flush();
                    bwFile.Close();
                }
            }
        }
    }
}