encrypt and decrypt md5 hash text

i am encrypting textbox value in md5 using this coding and passing as querystring , and on other page i want to decrypt.....


so plz tell how can i do this..



System.Security.Cryptography.MD5CryptoServiceProvider x = new System.Security.Cryptography.MD5CryptoServiceProvider();
        byte[] bs = System.Text.Encoding.UTF8.GetBytes(TextBox1.Text);
        bs = x.ComputeHash(bs);
        System.Text.StringBuilder s = new System.Text.StringBuilder();
        foreach (byte b in bs)
        {
            s.Append(b.ToString("x2").ToLower());
        }
        string password = s.ToString();
 & ...