AES Encryption/Decryption on C#

AESEnDecryption.cs

using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;
using System.Runtime.Serialization.Formatters.Binary;

class AESEnDecryption
{
    public static byte[] encrypt(byte[] bytes, string keyStr, string ivStr)
    {
        MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
        SHA256CryptoServiceProvider sha256 = new SHA256CryptoServiceProvider();
        byte[] ivBytes = md5.ComputeHash(Encoding.UTF8.GetBytes(ivStr));
        byte[] keyBytes = sha256.ComputeHash(Encoding.UTF8.GetBytes(keyStr));

        return encrypt(bytes, keyBytes, ivBytes);
    }

    static byte[] encrypt(byte[] bytes, byte[] keyBytes, byte[] ivBytes)
    {
        //RijndaelManaged aes = new RijndaelManaged();
        AesCryptoServiceProvider aes = new AesCryptoServiceProvider();

        aes.IV = ivBytes;
        aes.Key = keyBytes;
        //aes.Mode = CipherMode.CBC;
        //aes.Padding = PaddingMode.PKCS7;

        ICryptoTransform transform = aes.CreateEncryptor();
        return transform.TransformFinalBlock(bytes, 0, bytes.Length);
    }
    
    public static byte[] decrypt(byte[] bytes, string keyStr, string ivStr)
    {
        MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
        SHA256CryptoServiceProvider sha256 = new SHA256CryptoServiceProvider();
        byte[] ivBytes = md5.ComputeHash(Encoding.UTF8.GetBytes(ivStr));
        byte[] keyBytes = sha256.ComputeHash(Encoding.UTF8.GetBytes(keyStr));

        return decrypt(bytes, keyBytes, ivBytes);
    }

    static byte[] decrypt(byte[] bytes, byte[] keyBytes, byte[] ivBytes)
    {
        //RijndaelManaged aes = new RijndaelManaged();
        AesCryptoServiceProvider aes = new AesCryptoServiceProvider();

        aes.IV = ivBytes;
        aes.Key = keyBytes;
        //aes.Mode = CipherMode.CBC;
        //aes.Padding = PaddingMode.PKCS7;

        ICryptoTransform transform = aes.CreateDecryptor();
        return transform.TransformFinalBlock(bytes, 0, bytes.Length);
    }    

    public static string encryptStrAndToBase64(string enStr, string keyStr, string ivStr)
    {
        byte[] bytes = encrypt(Encoding.UTF8.GetBytes(enStr), keyStr, ivStr);
        return Convert.ToBase64String(bytes);
    }
    
    public static string decryptStrAndFromBase64(string deStr, string keyStr, string ivStr)
    {
        byte[] bytes = decrypt(Convert.FromBase64String(deStr), keyStr, ivStr);
        return Encoding.UTF8.GetString(bytes);
    }

    public void BinarySaveObjectWithAes<T>(T theObject, string fileName, string ivStr, string keyStr)
    {
        Stream streamWrite = File.Create(fileName);
        MemoryStream memoryStreamWrite = new MemoryStream();
        BinaryFormatter binaryWrite = new BinaryFormatter();
        binaryWrite.Serialize(memoryStreamWrite, theObject);
        memoryStreamWrite = new MemoryStream(encrypt(memoryStreamWrite.ToArray(), keyStr, ivStr));
        memoryStreamWrite.WriteTo(streamWrite);
        memoryStreamWrite.Close();
        streamWrite.Close();
    }

    public T BinaryReadObjectWithAes<T>(string fileName, string ivStr, string keyStr)
    {
        Stream streamRead = File.OpenRead(fileName);
        MemoryStream memoryStreamRead = new MemoryStream();
        BinaryFormatter binaryRead = new BinaryFormatter();
        streamRead.CopyTo(memoryStreamRead);
        memoryStreamRead = new MemoryStream(decrypt(memoryStreamRead.ToArray(), keyStr, ivStr));
        T theObject = (T)binaryRead.Deserialize(memoryStreamRead);
        streamRead.Close();
        memoryStreamRead.Close();
        return theObject;
    }
}