How to compare encrypted password in sql
string userName = txtusername.Text;
string password = txtpassword.Text;
Encryptor en = new Encryptor(EncryptionAlgorithm.Rc2, CreateRandomPassword(7));
password = en.Encrypt(password);
DataTable dt = uMManager.ValidateUser(userName, password);

private static string CreateRandomPassword(int passwordLength)
{
  string allowedChars = "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ0123456789!@$?_-";
  char[] chars = new char[passwordLength];
  Random rd = new Random();

  for (int i = 0; i < passwordLength; i++)
  {
     chars[i] = allowedChars[rd.Next(0, allowedChars.Length)];
  }
  return new string(chars);
}

public class Encryptor
    {
        EncryptEngine engin;
        public byte[] IV;

        public Encryptor(EncryptionAlgorithm algID, string key)
        {
            engin = new EncryptEngine(algID, key);
        }

        public EncryptEngine EncryptEngine
        {
            get
            {
                return engin;
            }
            set
            {
                engin = value;
            }
        }

        public string Encrypt(string MainString)
        {
            MemoryStream memory = new MemoryStream();
            CryptoStream stream = new CryptoStream(memory, engin.GetCryptTransform(), CryptoStreamMode.Write);
            StreamWriter streamwriter = new StreamWriter(stream);
            streamwriter.WriteLine(MainString);
            streamwriter.Close();
            stream.Close();
            IV = engin.Vector;
            byte[] buffer = memory.ToArray();
            memory.Close();
            return Convert.ToBase64String(buffer);

        }
    }