working aes encryption/decryption, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Security.Cryptography;
using System.Text;
    
namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            //Your code goes here
            
            var pomocna = new Program();
            
            var text = pomocna.Encryptxx("87bdd7da-f8e8-42d9-9bef-c08d67ed4d5621AWGHHXTM0X");
            Console.WriteLine("vysledok = " + text);
            
            
            var text3 = pomocna.Decryptxx(text);
            Console.WriteLine("vysledok = " + text3);
            
        }

public string Encryptxx(string text)
        {

byte[] src = Encoding.UTF8.GetBytes(text);
            byte[] key = Encoding.ASCII.GetBytes("0123456789abcdef");
            RijndaelManaged aes = new RijndaelManaged();
            aes.Mode = CipherMode.ECB;
            aes.Padding = PaddingMode.PKCS7;
            aes.KeySize = 128;

using (ICryptoTransform encrypt = aes.CreateEncryptor(key, null))
            {
                byte[] dest = encrypt.TransformFinalBlock(src, 0, src.Length);
                encrypt.Dispose();
                return Convert.ToBase64String(dest);
            }
        }

public string Decryptxx(string text)
        {

byte[] src = Convert.FromBase64String(text);
            RijndaelManaged aes = new RijndaelManaged();
            byte[] key = Encoding.ASCII.GetBytes("0123456789abcdef");
            aes.KeySize = 128;
            aes.Padding = PaddingMode.PKCS7;
            aes.Mode = CipherMode.ECB;
            using (ICryptoTransform decrypt = aes.CreateDecryptor(key, null))
            {
                byte[] dest = decrypt.TransformFinalBlock(src, 0, src.Length);
                decrypt.Dispose();
                return Encoding.UTF8.GetString(dest);
            }
        }
    
    }
    
    
}

Show compiler warnings [ + ] Show input
Compilation time: 0,14 sec, absolute running time: 0,11 sec, cpu time: 0,09 sec, average memory usage: 12 Mb, average nr of threads: 2