What is the problem ? Incorrect syntax near '='. Must declare the scalar variable "@Password".

protected void btnRegister_Click(object sender, EventArgs e)
{
    string cs = @"Data Source=.\SQLEXPRESS; 
                AttachDbFilename=|DataDirectory|\Database.mdf; 
                Integrated Security=True; 
                User Instance=True";

    string sql = "INSERT INTO Member (Username, UserPassword, Name, IC, Gender, Address, Email) VALUES (@Username, @Password, @Name, @IC, @Gender, @Address, @Email)";

    SqlConnection con = new SqlConnection(cs);
    SqlCommand cmd = new SqlCommand(sql, con);

    cmd.Parameters.AddWithValue("@Username", txtUsername.Text);
    cmd.Parameters.AddWithValue(Encrypt("@Password"), txtPassword.Text);
    cmd.Parameters.AddWithValue("@Name", txtName.Text);
    cmd.Parameters.AddWithValue("@IC", txtIC.Text);
    cmd.Parameters.AddWithValue("@Gender", ddlGender.Text);
    cmd.Parameters.AddWithValue("@Address", txtAddress.Text);
    cmd.Parameters.AddWithValue("@Email", txtEmail.Text);

    con.Open();        
    int number =  cmd.ExecuteNonQuery();//this line has a problem
    con.Close();

    if (number >= 1)
    {
        lblResult.Text = number + " Success Insert";
    }
    else
    {
        lblResult.Text = "Please try again";
    }
}

private string Encrypt(string clearText)
{
    string EncryptionKey = "MAKV2SPBNI99212";
    byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
    using (Aes encryptor = Aes.Create())
    {
        Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
        encryptor.Key = pdb.GetBytes(32);
        encryptor.IV = pdb.GetBytes(16);
        using (MemoryStream ms = new MemoryStream())
        {
            using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
            {
                cs.Write(clearBytes, 0, clearBytes.Length);
                cs.Close();
            }
            clearText = Convert.ToBase64String(ms.ToArray());
        }
    }
    return clearText;
}