PortBlog.API/Shared/KBR.Shared/Extensions/ConfigurationExtensions.cs

using Microsoft.Extensions.Configuration;
using System.Security.Cryptography;

namespace KBR.Shared.Extensions
{
    public static class ConfigurationExtensions
    {
        public static string DecryptConnectionString(this IConfiguration configuration, string encryptedConnectionString)
        {
            // Fix: Use GetSection and Value instead of GetValue (since GetValue is not available on IConfiguration)
            string keyBase64 = configuration.GetSection("ConnectionStrings:Key").Value;

            string vectorBase64 = encryptedConnectionString.Split(":")[1];
            string cipherText = encryptedConnectionString.Split(":")[0];

            using (Aes aesAlgorithm = Aes.Create())
            {
                aesAlgorithm.Key = Convert.FromBase64String(keyBase64);
                aesAlgorithm.IV = Convert.FromBase64String(vectorBase64);

                Console.WriteLine($"Aes Cipher Mode : {aesAlgorithm.Mode}");
                Console.WriteLine($"Aes Padding Mode: {aesAlgorithm.Padding}");
                Console.WriteLine($"Aes Key Size : {aesAlgorithm.KeySize}");
                Console.WriteLine($"Aes Block Size : {aesAlgorithm.BlockSize}");


                // Create decryptor object
                ICryptoTransform decryptor = aesAlgorithm.CreateDecryptor();

                byte[] cipher = Convert.FromBase64String(cipherText);

                //Decryption will be done in a memory stream through a CryptoStream object
                using (MemoryStream ms = new MemoryStream(cipher))
                {
                    using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
                    {
                        using (StreamReader sr = new StreamReader(cs))
                        {
                            return sr.ReadToEnd();
                        }
                    }
                }
            }
        }
    }
}