Multiple Root Declarition In Xml File during Serialization

i am doing Xml serialization but stuck in one error which i have almost one week i have simple web page like

FirstNameTextBox: LastNameTextBox: EmailTextBox:

SubmitButton

i have two classes called Customer and a Customer List the customer Class look like this

namespace XmlSearlizeProject.Classes
{
    [Serializable]
    [XmlRoot("CustomerData")]
    public class Customer
    {
        string id = default(string);
        string firstName = default(string);
        string lastName = default(string);
        string email = default(string);
        public Customer()
        {

        }
        public Customer(string id, string firstName, string lastName, string email)
        {
            CustomerId = id;
            FirstName = firstName;
            LastName = lastName;
            Email = email;

        }
        [XmlElement("CustomerId")]
        public string CustomerId
        {
            get
            {
                return this.id;
            }
            set
            {
                this.id = value;
            }
        }
        [XmlElement("FirstName")]
        public string FirstName
        {
            get
            {
                return this.firstName;
            }
            set
            {
                this.firstName = value;
            }
        }
         [XmlElement("LastName")]
        public string LastName
        {
            get
            {
                return this.lastName;
            }
            set
            {
                this.lastName = value;
            }
        }
         [XmlElement("CustomerEmail")]
        public string Email
        {
            get
            {
                return this.email;
            }
            set
            {
                this.email = value;
            }
        }
    }
}

and a CustomerList Class Look Like this

namespace XmlSearlizeProject.Classes
{
    [Serializable]
    public class CustomerList:List<Customer>
    {
    }
}

and the code which perform XML Serialization is:

namespace XmlSearlizeProject.WebPages
{
    public partial class CustomerPage : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        private void GeneralFunction(Stream xmlStream)
        {
            string customerId = Guid.NewGuid().ToString();
            Classes.CustomerList customerList = new Classes.CustomerList{ 
    new Classes.Customer
    {
        FirstName = this.FirstNameTextBox.Text,
        LastName = this.LastNameTextBox.Text,
        Email = this.EmailTextBox.Text,
        CustomerId = customerId
    }
};


            Classes.Customer customer = new Classes.Customer();
            XmlSerializer xmlSerializer = new XmlSerializer(typeof(Classes.CustomerList));
            XmlDocument document = new XmlDocument();
            document.Load(xmlStream);

            XmlElement id = document.CreateElement("Id");
            id.InnerText = customerId;
            document.DocumentElement.InsertAfter(id, document.DocumentElement.LastChild);

            XmlElement firstName = document.CreateElement("FirstName");
            firstName.InnerText = customer.FirstName;
            document.DocumentElement.InsertAfter(firstName, document.DocumentElement.LastChild);

            XmlElement lastName = document.CreateElement("LastName");
            lastName.InnerText = customer.LastName;
            document.DocumentElement.InsertAfter(lastName, document.DocumentElement.LastChild);

            XmlElement email = document.CreateElement("Email");
            email.InnerText = customer.Email;
            document.DocumentElement.InsertAfter(email, document.DocumentElement.LastChild);
            XmlTextWriter xmlTextWriter = new XmlTextWriter(xmlStream, Encoding.UTF8);
            xmlSerializer.Serialize(xmlTextWriter, customerList);
            xmlStream.Close();
        }

        private void SerializeCustomer()
        {

                Stream xmlWriterStream = new FileStream(Server.MapPath("~/Customer.xml"), FileMode.OpenOrCreate, FileAccess.ReadWri开发者_JS百科te);
                GeneralFunction(xmlWriterStream);
                xmlWriterStream.Close();
        }


        protected void SubmitButton_Click(object sender, EventArgs e)
        {
            SerializeCustomer();
        }
    }
}

and now my problem is this when i add first customer using Serialization Function then my XML File look like this

<?xml version="1.0" encoding="utf-8"?>
<ArrayOfCustomer xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Customer>
    <CustomerId>34f15068-4331-4253-8660-d1ce2199ed6d</CustomerId>
    <FirstName>haseeb</FirstName>
    <LastName>khan</LastName>
    <CustomerEmail>abc@hotmtail.com</CustomerEmail>
  </Customer>
</ArrayOfCustomer>

But when i try to add another Customer using the same Serialization Function with the same web page then my XML file look like this

<?xml version="1.0" encoding="utf-8"?>
<ArrayOfCustomer xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Customer>
    <CustomerId>34f15068-4331-4253-8660-d1ce2199ed6d</CustomerId>
    <FirstName>haseeb</FirstName>
    <LastName>khan</LastName>
    <CustomerEmail>abc@hotmtail.com</CustomerEmail>
  </Customer>
</ArrayOfCustomer><?xml version="1.0" encoding="utf-8"?>
<ArrayOfCustomer xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Customer>
    <CustomerId>924e5fe3-d5ce-41c2-a850-4d3da1e44f91</CustomerId>
    <FirstName>ammar</FirstName>
    <LastName>khan</LastName>
    <CustomerEmail>xyz@hotmail.com</CustomerEmail>
  </Customer>
</ArrayOfCustomer>

i am not understanding that how to fix this error i need my Xml File Like this when i ever i Add New Customer

<?xml version="1.0" encoding="utf-8"?>
<ArrayOfCustomer xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Customer>
    <CustomerId>34f15068-4331-4253-8660-d1ce2199ed6d</CustomerId>
    <FirstName>haseeb</FirstName>
    <LastName>khan</LastName>
    <CustomerEmail>abc@hotmtail.com</CustomerEmail>
  </Customer>
  <Customer>
    <CustomerId>924e5fe3-d5ce-41c2-a850-4d3da1e44f91</CustomerId>
    <FirstName>ammar</FirstName>
    <LastName>khan</LastName>
    <CustomerEmail>xyz@hotmail.com</CustomerEmail>
  </Customer>
</ArrayOfCustomer>

please help i am having this problem for one week and i have tried every thing but able to solve this error if anyone help me i will be thankful to him