XML Serialization with Array

Question

Introduction

My goal is to convert a LIST into XML format. This list will consist of several "REPORT" nodes all with child elements.I am using XML Serialization to achieve this result.

The resulting XML, will appear as this:

<ReportInfo>
      <ReportId>898899473</ReportId>
      <ReportType>_GET_MERCHANT_LISTINGS_DATA_</ReportType>
      <ReportRequestId>2278662938</ReportRequestId>
      <AvailableDate>2009-02-10T09:22:33+00:00</AvailableDate>
      <Acknowledged>false</Acknowledged>
    </ReportInfo>
<ReportInfo>
          <ReportId>894899473</ReportId>
          <ReportType>_GET_MERCHANT_LISTINGS_DATA_</ReportType>
          <ReportRequestId>227162938</ReportRequestId>
          <AvailableDate>2009-02-10T09:22:33+00:00</AvailableDate>
          <Acknowledged>false</Acknowledged>
        </ReportInfo>

ERROR:

ERROR:Object reference not set to an instance of an object.

reportXML.Report[index].ReportID = reportInfo.ReportId;

CODE(1):

/**********************************LOOP THROUGH LIST AND ADD TO XML****************************************************************************************/
                List<ReportInfo> reportInfoList = getReportListResult.ReportInfo;

                ReportListCatalog reportXML = new ReportListCatalog();

                int index = -1;
                foreach (ReportInfo reportInfo in reportInfoList)
                {

                    index++;
                    HttpContext.Current.Response.Write("ReportInfo");
                    if (reportInfo.IsSetReportId())
                    {
                         HttpContext.Current.Response.Write("ReportId");
                         HttpContext.Current.Response.Write("" +  reportInfo.ReportId);
                         reportXML.Report[index].ReportID = reportInfo.ReportId;
                         reportXML.Report[index].ReportID = reportInfo.ReportId;

                    }
                    if (reportInfo.IsSetReportType())
                    {
                         HttpContext.Current.Response.Write("                    ReportType");
                         HttpContext.Current.Response.Write("" +  reportInfo.ReportType);
                         reportXML.Report[index].ReportType = reportInfo.ReportType;

                    }
                    if (reportInfo.IsSetReportRequestId())
                    {
                         HttpContext.Current.Response.Write("                    ReportRequestId");
                         HttpContext.Current.Response.Write("" +  reportInfo.ReportRequestId);
                         reportXML.Report[index].ReportRequestId = reportInfo.ReportRequestId;

                    }
                    if (reportInfo.IsSetAvailableDate())
                    {
                         HttpContext.Current.Response.Write("                    AvailableDate");
                         HttpContext.Current.Response.Write("" +  reportInfo.AvailableDate);
                         reportXML.Report[index].ReportDate = reportInfo.AvailableDate;

                    }
                    if (reportInfo.IsSetAcknowledged())
                    {
                         HttpContext.Current.Response.Write("                    Acknowledged");
                         HttpContext.Current.Response.Write("" +  reportInfo.Acknowledged);
                         reportXML.Report[index].ReportAcknowledged = reportInfo.Acknowledged;
                    }

                }
                reportXML.SerializeToXML(reportXML);


            }

My XML Class and Serialization Function:

namespace AmazonWebService.Model
{
/***********************************************************************************/
    [XmlRoot("ReportListCatalog")]
    public class ReportListCatalog
    {
        [XmlArray("Report")]
        public amzReport[] Report;
        public class amzReport
        {
            [XmlArrayItem("ReportID")]
            public String ReportID
            { get; set; }

            [XmlArrayItem("ReportType")]
            public String ReportType
            { get; set; }

            [XmlArrayItem("ReportRequestId")]
            public String ReportRequestId
            { get; set; }

            [XmlArrayItem("AvailibleDate")]
            public System.DateTime ReportDate
            { get; set; }

            [XmlArrayItem("Acknowledged")]
            public Boolean ReportAcknowledged
            { get; set; }
        }

        /********************************************************************************/
        public  void SerializeToXML(ReportListCatalog amzReport)
        {
            String SaveDir = "\\" + System.Web.HttpRuntime.AppDomainAppPath.ToString();
            String dt = System.DateTime.Now.ToString("yyyy_dd_mm_hh_mm");
            XmlSerializer serializer = new XmlSerializer(typeof(List<amzReport>));
            TextWriter textWriter = new StreamWriter(SaveDir + dt + ".xml");
            serializer.Serialize(textWriter, amzReport);
            textWriter.Close();
        }
        /********************************************************************************/


    }

Answer 1

well, you are doing this wrong - you should probably use XML serialization - see this page for example: http://msdn.microsoft.com/en-us/library/182eeyhh.aspx

BUT in your code the error is that you create EMPTY array here:

public amzReport[] Report;

and you never "expand" it. I would suggest you change that line to

public List<amzReport> Report;

and then change your main foreach loop like this:

foreach (ReportInfo reportInfo in reportInfoList)
{
    amzReport rpt = new amzReport();

    index++;
    HttpContext.Current.Response.Write("ReportInfo");
    if (reportInfo.IsSetReportId())
    {
         HttpContext.Current.Response.Write("ReportId");
         HttpContext.Current.Response.Write("" +  reportInfo.ReportId);
         rpt.ReportID = reportInfo.ReportId;
    }

    // all other code goes here...

    reportXML.Report.Add(rpt);
}