C # DES encryption and decryption

using System;
using System.Text;
using System.Security.Cryptography;
using System.Diagnostics;
using System.IO;
using System.Reflection;
using System.Windows.Forms;

namespace FirstEliteCSFileEncoder
{
    class Program
    {
        ///  <Summary> 
        /// DESEncrypt encryption and decryption algorithms.
        ///  </ Summary> 
        public  class DESEncoder
        {
            public DESEncoder(string key)
            {
                this.Key = key;
            }

            ///  <Summary> 
            /// key for the symmetric encryption and decryption
             ///  </ Summary> 
            public  String Key { GET ; Private  SET ;}

            /// <summary>
            /// DES加密
            /// </summary>
            /// <param name="encryptString"></param>
            /// <returns></returns>
            public string EncryptString(string encryptString)
            {
                byte[] keyBytes = Encoding.UTF8.GetBytes(this.Key.Substring(0, 8));
                byte[] keyIV = keyBytes;
                byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
                DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
                MemoryStream mStream = new MemoryStream();
                CryptoStream cStream = new CryptoStream(mStream, provider.CreateEncryptor(keyBytes, keyIV), CryptoStreamMode.Write);
                cStream.Write(inputByteArray, 0, inputByteArray.Length);
                cStream.FlushFinalBlock();
                return Convert.ToBase64String(mStream.ToArray());
            }

            /// <summary>
            /// DES解密
            /// </summary>
            /// <param name="decryptString"></param>
            /// <returns></returns>
            public string DecryptString(string decryptString)
            {
                byte[] keyBytes = Encoding.UTF8.GetBytes(this.Key.Substring(0, 8));
                byte[] keyIV = keyBytes;
                byte[] inputByteArray = Convert.FromBase64String(decryptString);
                DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
                MemoryStream mStream = new MemoryStream();
                CryptoStream cStream = new CryptoStream(mStream, provider.CreateDecryptor(keyBytes, keyIV), CryptoStreamMode.Write);
                cStream.Write(inputByteArray, 0, inputByteArray.Length);
                cStream.FlushFinalBlock();
                return Encoding.UTF8.GetString(mStream.ToArray());
            }

            public bool EncryptFile(string filepath)
            {
                try
                {
                    var bytes = File.ReadAllBytes(filepath);
                    File.WriteAllBytes(filepath, Encoding.UTF8.GetBytes(this.EncryptString(Convert.ToBase64String(bytes))));
                    return true;
                }
                catch (Exception ex)
                {
                    Debug.Print(ex.ToString());
                    return false;
                }
            }

            public bool DecryptFile(string filepath)
            {
                try
                {
                    var bytes = File.ReadAllBytes(filepath);
                    File.WriteAllBytes(filepath, Convert.FromBase64String(this.DecryptString(Encoding.UTF8.GetString(bytes))));
                    return true;
                }
                catch (Exception ex)
                {
                    Debug.Print(ex.ToString());
                    return false;
                }
            }
        }

        public static bool LoadAssembly(string filepath)
        {
            try
            {
                var encoder = new DESEncoder("$u&CIbzz");
                var bytes = File.ReadAllBytes(filepath);
                var assembly = Assembly.Load(Convert.FromBase64String(encoder.DecryptString(Encoding.UTF8.GetString(bytes))));
                MessageBox.Show(assembly.FullName);
                return true;
            }
            catch (Exception ex)
            {
                Debug.Print(ex.ToString());
                return false;
            }
        }

        static void Main(string[] args)
        {
            LoadAssembly(@"");
            var encoder = new DESEncoder("$u&CIbzz");
            encoder.EncryptFile(@"C:\Users\knife\Desktop\翻译.txt");
            encoder.DecryptFile(@"C:\Users\knife\Desktop\翻译.txt");
            Console.WriteLine("over");
            Console.ReadLine();
        }

        
    }
}