文件的加密和解密在解密时导致一个空白文件

下面是我用来测试文件加密和解密的一个简单代码片段。发生的事情是加密工作正常-然而，当我解密时，文件是空白的，我不完全确定为什么。

我也得到了一个"填充无效，不能被删除"的问题，但我可以用Padding.None解决这个问题，但我不明白为什么解密时文件为空。我用一个简单的文本文档来测试。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;
using System.IO;
namespace EncryptionTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var Mode = "";
            bool Loop = true;
            while (Loop)
            {
                Console.WriteLine("Encrypt or Decrypt? (E/D)");
                Mode = Console.ReadLine();
                if (Mode.ToUpper() == "E" || Mode.ToUpper() == "D")
                    switch (Mode.ToUpper())
                    {
                        case "E":
                            Mode = "Encrypt";
                            Loop = false;
                            continue;
                        case "D":
                            Mode = "Decrpt";
                            Loop = false;
                            continue;
                    }
                else
                    Console.WriteLine("Must be E OR D");
            }
            Console.WriteLine("What directory do you want to encrypt?");
            var fileDirectory = Console.ReadLine();
            Console.WriteLine("What password do you want to use?");
            var passWord = Console.ReadLine();
            string[] files = Directory.GetFiles(fileDirectory);
            for (int i = 0; i < files.Length; i++)
            {
                byte[] bytesToBeEncrypted = File.ReadAllBytes(files[i]);
                byte[] passwordBytes = Encoding.UTF8.GetBytes(passWord);
                // Hash the password with SHA256
                passwordBytes = SHA256.Create().ComputeHash(passwordBytes);
                byte[] bytesCyrpt = new byte[0];
                if (Mode == "Encrypt")
                {
                    bytesCyrpt = AES_Encrypt(bytesCyrpt, passwordBytes);
                    File.WriteAllBytes(encryptedFileName(files[i]), bytesCyrpt);
                    File.Delete(files[i]);
                }
                else
                {
                    bytesCyrpt = AES_Decrypt(bytesCyrpt, passwordBytes);
                    File.WriteAllBytes(decryptFileName(files[i]), bytesCyrpt);
                }                  
            }
        }
        public static byte[] AES_Encrypt(byte[] bytesToBeEncrypted, byte[] passwordBytes)
        {
            byte[] encryptedBytes = null;
            // Set your salt here, change it to meet your flavor:
            // The salt bytes must be at least 8 bytes.
            byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };
            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 256;
                    AES.BlockSize = 128;
                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    AES.IV = key.GetBytes(AES.BlockSize / 8);
                    AES.Mode = CipherMode.CBC;
                    using (var cs = new CryptoStream(ms, AES.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeEncrypted, 0, bytesToBeEncrypted.Length);
                        cs.Close();
                    }
                    encryptedBytes = ms.ToArray();
                }
            }
            return encryptedBytes;
        }
        public static byte[] AES_Decrypt(byte[] bytesToBeDecrypted, byte[] passwordBytes)
        {
            byte[] decryptedBytes = null;
            // Set your salt here, change it to meet your flavor:
            // The salt bytes must be at least 8 bytes.
            byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };
            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 256;
                    AES.BlockSize = 128;
                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    AES.IV = key.GetBytes(AES.BlockSize / 8);
                    AES.Mode = CipherMode.CBC;
                    using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeDecrypted, 0, bytesToBeDecrypted.Length);
                        cs.Close();
                    }
                    decryptedBytes = ms.ToArray();
                }
            }
            return decryptedBytes;
        }
        private static string encryptedFileName(string fileName)
        {
            string new_file_name = string.Empty;
            string extension = fileName.Split('.').Last();
            new_file_name = fileName.Replace(extension, "");
            new_file_name = new_file_name + "_encrypt." + extension;
            return new_file_name;
        }
        private static string decryptFileName(string fileName)
        {
            string new_file_name = fileName;
            new_file_name = new_file_name.Replace("_encrypt", "");
            return new_file_name;
        }
    }
}

byte[] bytesToBeEncrypted = File.ReadAllBytes(files[i]);
byte[] passwordBytes = Encoding.UTF8.GetBytes(passWord);
// Hash the password with SHA256
passwordBytes = SHA256.Create().ComputeHash(passwordBytes);
byte[] bytesCyrpt = new byte[0];
if (Mode == "Encrypt")
{
    bytesCyrpt = AES_Encrypt(bytesToBeEncrypted, passwordBytes);
    File.WriteAllBytes(encryptedFileName(files[i]), bytesCyrpt);
    File.Delete(files[i]);
}
else
{
    bytesCyrpt = AES_Decrypt(bytesToBeEncrypted, passwordBytes);
    File.WriteAllBytes(decryptFileName(files[i]), bytesCyrpt);
}