Adding to a List causing null reference

Question

I have a class which models the format of the CSV being uploaded (I'm using the FileHelpers library):

[DelimitedRecord(",")]
public class CSVModel
{
    [FieldQuoted('"', QuoteMode.OptionalForBoth, MultilineMode.NotAllow)]
    public string Field1;
    [FieldQuoted('"', QuoteMode.OptionalForBoth, MultilineMode.NotAllow)]
    public string Field2;
}

Then I have a class to display the result of the upload after I've parsed the file row-by-row:

public class UploadResult
{
    public List<CSVModel> InvalidField;
    public List<CSVModel> Valid;
}

I won't go into detail about how I implement FileHelpers because it all works - a file can be uploaded successfully - it only breaks when I try add an instance of the CSV model to a list like so:

public static UploadResult ProcessCSV(CSVModel[] records)
{
    UploadResult uploadResult = new UploadResult();

    for (int i = 1; i < records.Length; i++)
    {
        CSVModel csvModel = records[i];

        // check stuff

        uploadResult.Valid.Add(csvModel); // this is where it breaks
    }

    return uploadResult;
}

The exception is giving me nothing more than null reference. What could I be doing incorrectly?

edit: When I debug, 'csvModel' is definitely not null when I try add it to the List

Is uploadResult.Valid null?

Blorgbeard
– Blorgbeard

2013-07-09 20:25:45 +00:00
Commented Jul 9, 2013 at 20:25 — Blorgbeard
– Blorgbeard, Commented Jul 9, 2013 at 20:25

Tim Schmelter · Accepted Answer · 2013-07-09 20:25:52Z

2

Valid is null, you have to initialize it:

public class UploadResult
{
    public List<CSVModel> InvalidField = new List<CSVModel>();
    public List<CSVModel> Valid = new List<CSVModel>();
}

or via constructor:

public class UploadResult
{
    public UploadResult()
    {
        InvalidField =  new List<CSVModel>();
        Valid =  new List<CSVModel>();
    }
    public List<CSVModel> InvalidField;
    public List<CSVModel> Valid;
}

answered Jul 9, 2013 at 20:25

Tim Schmelter

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1 Comment

notAnonymousAnymore Over a year ago

Can only accept the answer in 12 minutes, but this solved it, thanks

mao47 · Accepted Answer · 2013-07-09 20:26:42Z

1

You are initializing UploadResult but not the List properties. Try something like this:

UploadResult uploadResult = new UploadResult {
    InvalidField = new List<CSVModel>(),
    Valid = new List<CSVModel>()
};

answered Jul 9, 2013 at 20:26

mao47

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1 Comment

mao47 Over a year ago

If you do this and use UploadResult somewhere else, you'll need to remember to initialize the lists. @Tim's method is probably better.

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