System.InvalidOperationException

[lexavision]

Hi,

I get an exception when I run this 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?

[BigEd781]

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.

[lexavision]

Thanks BigED!!!

Resulting 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());
        }

[BigEd781]

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

// 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");

[lexavision]

I will follow your advise... Thanks Again!