C# ASP.NET Byte Array NullReferenceException

[foggyfury]

Hi, I think I am having a null reference with "encrypted". How do I solve this. The code works in windows form with encrypt and decrypt both working.

    byte[] encrypted;
    protected void BnEncrypt_Click(object sender, EventArgs e)
    {
 
        MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
        UTF8Encoding utf8 = new UTF8Encoding();
        TripleDESCryptoServiceProvider tDES = new TripleDESCryptoServiceProvider();
        tDES.Key = md5.ComputeHash(utf8.GetBytes(TextBox1.Text));
        tDES.Mode = CipherMode.ECB;
        tDES.Padding = PaddingMode.PKCS7;
        ICryptoTransform trans = tDES.CreateEncryptor();
        encrypted = trans.TransformFinalBlock(utf8.GetBytes(TextBox2.Text), 0, utf8.GetBytes(TextBox2.Text).Length);
        TextBox3.Text = BitConverter.ToString(encrypted);
 
    }
 
    protected void BnDecrypt_Click(object sender, EventArgs e)
    {
 
        MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
        UTF8Encoding utf8 = new UTF8Encoding();
        TripleDESCryptoServiceProvider tDES = new TripleDESCryptoServiceProvider();
        tDES.Key = md5.ComputeHash(utf8.GetBytes(TextBox4.Text));
        tDES.Mode = CipherMode.ECB;
        tDES.Padding = PaddingMode.PKCS7;
        ICryptoTransform trans = tDES.CreateDecryptor();
        TextBox5.Text = utf8.GetString(trans.TransformFinalBlock(encrypted, 0, encrypted.Length)); //This line throws the exception
 
    }