Encryption.cs

using System.IO;
using System.Text;
using System.Security.Cryptography;
using System;

public static class Encryption
{
    private static string prm_key = "wSoQm3jMNPYiUxdg0LCjIJw/vmr7Dn8h6VMe2OZR7uU=";
    private static string prm_iv = "WkhVCuBAbXxLJn5pG4eH/C1pSnCOoPdSrsx3zHEVG5g=";
    
    public static string Encrypt(string prm_text_to_encrypt)
    {
        var sToEncrypt = prm_text_to_encrypt;

        var rj = new RijndaelManaged()
        {
            Padding = PaddingMode.PKCS7,
            Mode = CipherMode.CBC,
            KeySize = 256,
            BlockSize = 256,
        };

        var key = Convert.FromBase64String(prm_key);
        var IV = Convert.FromBase64String(prm_iv);

        var encryptor = rj.CreateEncryptor(key, IV);

        var msEncrypt = new MemoryStream();
        var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write);

        var toEncrypt = Encoding.ASCII.GetBytes(sToEncrypt);

        csEncrypt.Write(toEncrypt, 0, toEncrypt.Length);
        csEncrypt.FlushFinalBlock();

        var encrypted = msEncrypt.ToArray();

        return (Convert.ToBase64String(encrypted));
    }

    public static string Decrypt(string prm_text_to_decrypt)
    {

        var sEncryptedString = prm_text_to_decrypt;

        var rj = new RijndaelManaged()
        {
            Padding = PaddingMode.PKCS7,
            Mode = CipherMode.CBC,
            KeySize = 256,
            BlockSize = 256,
        };

        var key = Convert.FromBase64String(prm_key);
        var IV = Convert.FromBase64String(prm_iv);

        var decryptor = rj.CreateDecryptor(key, IV);

        var sEncrypted = Convert.FromBase64String(sEncryptedString);

        var fromEncrypt = new byte[sEncrypted.Length];

        var msDecrypt = new MemoryStream(sEncrypted);
        var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read);

        csDecrypt.Read(fromEncrypt, 0, fromEncrypt.Length);

        return (Encoding.ASCII.GetString(fromEncrypt));
    }

    public static void GenerateKeyIV(out string key, out string IV)
    {
        var rj = new RijndaelManaged()
        {
            Padding = PaddingMode.PKCS7,
            Mode = CipherMode.CBC,
            KeySize = 256,
            BlockSize = 256,
        };
        rj.GenerateKey();
        rj.GenerateIV();

        key = Convert.ToBase64String(rj.Key);
        IV = Convert.ToBase64String(rj.IV);
    }
}