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We are trying to load data into an array using code given to us by the teacher. The code is given to us because we have not and will not learn any of it, but there seems to be a problem with it. Public void LoadData() is the method he gave to us. We were to add code to store it into our array.

What I have added is the two lines of code that are denoted with ** on either side. This was what the tutor instructed us to do, but they are also stumped with the problem we have. We keep getting the NullReferenceException was unhandled, object reference is not to an instance object error.

The tutors can’t seem to figure it out, and we searched the internet and worked for hours trying to find a solution. I’ll also add that when tinkering with possible solutions, the error would sometimes point to a different location. The solutions I have read don’t seem to be working. Some say it’s the way I may be declaring my array, and some say add something like if (r!=null) as a null check (which we have never learned anything about) I tried adjusting to their advice and either it didn’t work, or I’m just putting it in the wrong place.

Please take a look at the code and see what is missing. Please understand, we are in a fundamentals class. We don’t know what null checks are, what stack traces are, or anything advanced. I’ve excluded some methods that I know to be correct and would just clutter everything. You will see where I’ve created the array called scores, and the public void data that was copy and pasted.

It seems to be something wrong with the s and r variables that are in included in the LoadData() code, or the way I declared the scores array. Maybe it's something else.

using System; using System.Collections.Generic;

using System.Linq;
using System.IO;
using System.Text;
using System.Threading.Tasks;

namespace DataAnalysis
{
    class TestScores
    {
        int[] scores;
        private double[] counter;
        private int count;

        public TestScores()
        {
            count = 0;
            scores = new int[100];
            LoadData();
            for (int i = 0; i < scores.Length; i++)
            {
                count++;
            }
        }

        public void LoadData()
        {
            int i = 0;
            StreamReader r = null;
            string path = "C:\\IST600Work\\testscore.txt";
            String s;
            try
            {
                r = new StreamReader(path);
                while (!r.EndOfStream)
                {
                    s = r.ReadLine(); // Reads one testscore data, as a string                   
                    **scores[i] = int.Parse(s);
                    **
                        **i++;
                    **
                    // Add code here to store it to your array
                }
            }
            catch (FileNotFoundException n)
            {
                Console.WriteLine("File to read not found");
            }
            catch (IOException o)
            {
                Console.WriteLine(o.Message);
            }
            finally
            {
                r.Close();
                r.Dispose();
            }
        }
    }
}
Rob
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IEmpireOfTheSun
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  • What line is throwing the exception? – Abion47 Dec 10 '16 at 08:42
  • *Please understand, we are in a fundamentals class. We don’t know what null checks are, what stack traces are, or anything advanced* Then google it. There are thousands of questions about null reference exceptions. Stack overflow is *not* a debugging service. – Rob Dec 10 '16 at 08:43
  • Did you actually try to add the null checks into your code, as suggested by others? You should check s to not be null before using them – user1781290 Dec 10 '16 at 08:43
  • For lack of a response, my guess is that it's the lines in the finally clause that throw the error. This is because, if the constructor for `StreamReader` throws an error, then `r` will never get assigned, but the finally clause code gets called anyway. – Abion47 Dec 10 '16 at 08:54
  • @Abion47 at first it showed up on the scores[i] = int.Parse(s), then once I changed some thing it ended up on the r.close; line near the end. I forgot what I did to cause that, but now it shows up in a line of code in a method I didn't include here. – IEmpireOfTheSun Dec 10 '16 at 19:52
  • I couldn't tell you why it was throwing on `scores[i] = int.Parse(s);` (since I would have to see your code at that point to know), but it throwing on `r.Close();` means that what I said is likely correct - the `StreamReader` constructor is throwing an error and `r` is never getting assigned, so by the time the code reaches the finally clause, `r` is null. Add a null check around your finally code, i.e. `if (r != null) { ... }`. – Abion47 Dec 10 '16 at 19:56

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