CODEWITHSUNDEEP
c#
Alan2
Alan2

Reputation: 24572

Exception when creating a list saying:

I have the following code:

        try
        {
            var result =
           from entry in feed.Descendants(a + "entry")
           let content = entry.Element(a + "content")
           let properties = content.Element(m + "properties")
           let notes = properties.Element(d + "DetailsJSON")
           let questionMessage = properties.Element(d + "QuestionText")
           let title = properties.Element(d + "Title")
           let partitionKey = properties.Element(d + "PartitionKey")
           where partitionKey.Value == "0001I" && title != null
           select new Question
           {
               Notes = notes.Value ?? "n/a",
               Title = title.Value,
               QuestionMessage = questionMessage.Value
           };

            // xx
            IList<Question> resultx = null;
            foreach (var question in result)
            {
                resultx.Add(question);
            }
            // yy
            return result;

        }
        catch (Exception ex)
        {
            throw new InvalidOperationException("GetQuestions.Get problem", ex);
        };

If I comment out the part of the code between xx and yy then it works. Otherwise I get an exception saying:

ex  {"Object reference not set to an instance of an object."}   System.Exception {System.NullReferenceException}

Can someone give me some ideas about what I might be doing wrong?

Upvotes: 0

Views: 58

Answers (2)

Arian Motamedi
Arian Motamedi

Reputation: 7413

Your resultx is explicitly set to null, so upon resultx.Add() you get a NullReferenceException. You need to initialize the list first.

Upvotes: 1

Simon Whitehead
Simon Whitehead

Reputation: 65079

Your list is null, hence the NullReferenceException:

IList<Question> resultx = null;
foreach (var question in result)
{
    resultx.Add(question); // Ouch. resultx is set to null above here
}

You need to initialize the list to actually be a List<Question>, not null:

IList<Question resultx = new List<Question>();
// .. the rest of the code

Upvotes: 3

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