ASP.Net Export List to CSV

I have a very old asp.net application that uses C# .Net and JQuery Mobile, and I need to add 1 feature: Export a list of data to a csv file. Thus far, I have the UI stuff sorted out. I have a jquery button that passes a parameter in the request query string to indicate on page load that we need to export data to Excel. I also have the following C# in the page load event. Unfortunately, when I run this code in Visual Studio with Chrome (or any browser), I do not get a prompt to save the csv file. When I run it with IE, I get the following error:

"Unhandled exception at line 2371, column 4 in http://localhost:53748/js/libs/jquery-mobile/jquery.mobile-1.0a4.1.js

0x800a138f - Javascript runtime error:Unable to get property '_trigger' of undefined or null reference."

I'm not sure if I am handling everything with the response object correctly.

        if (Request.QueryString["isExportToExcelRequired"] == "true")
        {
            StringWriter sw = new StringWriter();
            sw.WriteLine("\"ItemID\",\"Description\",\"Price\"");

            if (MasterList.Count > 0)
            {
                for (int i = 0; i < MasterList.Count; i++)
                {
                    sw.WriteLine(string.Format("\"{0}\",\"{1}\",\"{2}\"",
                                               MasterList[i].item.ItemID,
                                               MasterList[i].item.ItemDesc,
                                               MasterList[i].P0
                                               ));
                }

                string fileName = string.Format("{0}_{1}", SubClassID, DateTime.UtcNow.ToString("dd-MM-yyyy"));

                // Write response. 
                Response.ClearContent();
                Response.AddHeader("content-disposition", "attachment;filename=" + fileName + ".csv");
                Response.ContentType = "text/csv";
                Response.Write(sw.ToString());
                Response.End();
            }
        }

I'd use csvHelper. It's a handy library. It's been around since 2009 so I'd imagine your application isn't too old to benefit from this library. Below is a basic example of going from List to CSV.

The error you're getting is because something that shouldn't be NULL is indeed NULL. Run it in visual studio and let it throw the exception. Go through the debugger and find what's NULL then go through the logic and discover why it didn't get set to a value.

void Export()
{
    using (var stream = new MemoryStream())
    using (var reader = new StreamReader(stream))
    using (var writer = new StreamWriter(stream))
    using (var csv = new CsvWriter(writer))
    {

        foreach (var item in MasterList)
        {
            foreach (var field in item)
            {
                csv.WriteField(field);
            }
            csv.NextRecord();
        }
        writer.Flush();
        stream.Position = 0;

        reader.ReadToEnd().Dump();
    }
}