System.InvalidOperationException

Hi,

I get an exception when I run this code:

Code:

---

        try
        {

            ArrayList arrayList = new ArrayList();
            TicketBL ticket = new TicketBL();
            arrayList = ticket.GetTicketsForOffline();

            FileStream fs = new FileStream(FILE_PATH, FileMode.Create);
            XmlSerializer serializer = new XmlSerializer(typeof(ArrayList));
            serializer.Serialize(fs, arrayList); <--System.InvalidOperationException: There was an error generating the XML document.
            fs.Close();
            MessageBox.Show("List Pull complete");
        }
        catch (Exception ex)
        {
            MessageBox.Show("Error Pulling list", ex.ToString());
        }

---

The file creates the .xml file but doesn't serialize the data.

Any thoughts?

1. Don't use ArrayList. That class has been obsolete since generics debuted in .NET 2.0
2. You cannot serialize an ArrayList, hence the InvalidOperation exception. ArrayList is not a typed collection and thus cannot be serialized directly. You can use a generic collection List<T> or convert the ArrayList to an array.

Thanks BigED!!!

Resulting code:

Code:

---

        try
        {

            TicketBL ticket = new TicketBL();
            ArrayList arrList = new ArrayList();
            arrList = ticket.GetTicketsForOffline();

            // Convert ArraList to List type
            List<TicketVO> listResult = new List<TicketVO>(arrList.Count);
            foreach (TicketVO tickets in arrList)
            {
                listResult.Add(tickets);
            } 
            FileStream fs = new FileStream(FILE_PATH, FileMode.Create);
            XmlSerializer serializer = new XmlSerializer(typeof(List<TicketVO>));
            serializer.Serialize(fs, listResult);
            fs.Close();
            MessageBox.Show("List Pull complete");

        }
        catch (Exception ex)
        {
            MessageBox.Show("Error Pulling list", ex.ToString());
        }

---

You're welcome. I would suggest a couple more changes though...

Code:

---

// I would make GetTicketsForOffline a static method instead of an instance method
ArrayList arrList = new TicketBL().GetTicketsForOffline();

// there are fancier ways to do this with LINQ, but this is fine
List<TicketVO> listResult = new List<TicketVO>();
foreach (TicketVO ticket in arrList)
{
    listResult.Add(ticket);
} 

// using this pattern ensures that the stream is disposed.
// if an error had occurred before you called Close previously
// you would have left the file with an open handle and perhaps
// not flushed the contents to disk.
using (FileStream fs = new FileStream(FILE_PATH, FileMode.Create))
{
    XmlSerializer serializer = new XmlSerializer(typeof(List<TicketVO>));
    serializer.Serialize(fs, listResult);
}

MessageBox.Show("List Pull complete");

---

I will follow your advise... Thanks Again!