C# Example of AES256 encryption using System.Security.Cryptography.Aes

Question

I need to implement AES 256 encryption /decryption and I haven\'t been able to find an example that works correctly.

MSDN suggests that I should use the AES class.

Answer 1

public class AesCryptoService
{
    private static byte[] Key = Encoding.ASCII.GetBytes(@"qwr{@^h`h&_`50/ja9!'dcmh3!uw<&=?");
    private static byte[] IV = Encoding.ASCII.GetBytes(@"9/\~V).A,lY&=t2b");


    public static string EncryptStringToBytes_Aes(string plainText)
    {
        if (plainText == null || plainText.Length <= 0)
            throw new ArgumentNullException("plainText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("IV");
        byte[] encrypted;


        using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
        {
            aesAlg.Key = Key;
            aesAlg.IV = IV;
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.Padding = PaddingMode.PKCS7;

            ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

            using (MemoryStream msEncrypt = new MemoryStream())
            {
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    {
                        swEncrypt.Write(plainText);
                    }
                    encrypted = msEncrypt.ToArray();
                }
            }
        }
        
        return Convert.ToBase64String(encrypted);
    }


    
    public static string DecryptStringFromBytes_Aes(string Text)
    {
        if (Text == null || Text.Length <= 0)
            throw new ArgumentNullException("cipherText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("IV");

        string plaintext = null;
        byte[] cipherText = Convert.FromBase64String(Text.Replace(' ', '+'));

        using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
        {
            aesAlg.Key = Key;
            aesAlg.IV = IV;
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.Padding = PaddingMode.PKCS7;


            ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

            using (MemoryStream msDecrypt = new MemoryStream(cipherText))
            {
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                    {
                        plaintext = srDecrypt.ReadToEnd();
                    }
                }
            }

        }

        return plaintext;
    }
}