Cant read text file of integers into an integer array

Question

This is driving me literally insane for some reason my code to read a simple text file of ints into an int array wont work.

private void HardButton_Click(object sender, EventArgs e)
    {
        int[] hard1 = { };
        int counter = 0;


        using (StreamReader inFile = new StreamReader("h1.txt"))
        {
            string str = null;

            while ((str = inFile.ReadLine()) != null)
            {
                hard1[counter] = Convert.ToInt32(str);
                counter++;
            }
        }

hard1 is an array of ints that i need to hold each integer placed into it by reading the text file. My error is that my array is out of bounds even though I'm iterating each time through the loop. I am at a loss.

EDIT: Here is the txt file input

You probably of more than one number on a line like : "1 2 3 4 5". So you need to split the numbers on the line to an array. — jdweng
– jdweng, Commented Apr 3, 2019 at 16:46
Do you understand what int[] hard1 = { }; does? i.e. what is the length of hard1? — TnTinMn
– TnTinMn, Commented Apr 3, 2019 at 17:01
Your array does not have a size. See learn.microsoft.com/en-us/dotnet/csharp/programming-guide/… — Andrew
– Andrew, Commented Apr 3, 2019 at 17:04

Joel Coehoorn · Accepted Answer · 2019-04-03 18:05:46Z

4

C#/.Net has real arrays, not the psuedo-array collections you see in so many other languages (it has those, too, it just doesn't try to pass them off as arrays). One attribute of real arrays is a fixed size.

So when you declare the array like this:

int[] hard1 = { };

what you have is an array fixed at size 0, and therefore assigning to the array later on like this:

hard1[counter] = Convert.ToInt32(str);

is assigning to nowhere.

You have many options to fix this. Here is one of them:

private void HardButton_Click(object sender, EventArgs e)
{
    var result = File.ReadLines("h1.txt").
         Where(line => !string.IsNullOrWhitespace(line)).
         Select(line => int.Parse(line)).
         ToArray();
}

edited Apr 3, 2019 at 18:05

answered Apr 3, 2019 at 17:01

Joel Coehoorn

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2 Comments

Trevor Johnson Over a year ago

Still got the same error: "input string was not in the correct format"

Joel Coehoorn Over a year ago

That's not same error. The old error was "Index was outside the bounds of the array." But I added a fix.

Geoffrey · Accepted Answer · 2019-04-03 17:43:26Z

1

If you don't know the length in advance... use a list.

private void HardButton_Click(object sender, EventArgs e)
{
    var hard1 = new List<int>();
    int counter = 0;


    using (StreamReader inFile = new StreamReader("h1.txt"))
    {
        string str = null;

        while ((str = inFile.ReadLine()) != null)
        {
            hard1.Add(Convert.ToInt32(str));
            counter++;
        }
    }
...

If you don't have complete control over the file it might be necessary to do extra controls before converting to int as well.

Is every line exactly one integer?
Do I need to trim?
Can there be empty lines?

answered Apr 3, 2019 at 17:43

Geoffrey

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Comments

Joel Coehoorn · Accepted Answer · 2019-04-03 18:12:23Z

0

Use this:

private void button1_Click(object sender, EventArgs e)
{
    int[] hard1 = { };

    var lines = File.ReadAllLines("h1.txt");
    var lineWithoutEmptySpace = lines.Where(x => !string.IsNullOrEmpty(x)).ToArray();
    hard1 = new Int32[lineWithoutEmptySpace.Length];

    for (var i = 0; i < lineWithoutEmptySpace.Length; i++)
    {
        hard1[i] = Convert.ToInt32(lineWithoutEmptySpace[i]);
    }
}

edited Apr 3, 2019 at 18:12

Joel Coehoorn

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answered Apr 3, 2019 at 18:09

Adrian Tocu

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3 Comments

Joel Coehoorn Over a year ago

This will work, but it's still very wasteful code: the = { } creates a new empty object that will be immediately thrown away; ReadAlllLines() vs ReadLines() forces the entire file into an array in memory at the same time, even though that array will be discarded almost immediately and the .Where() method works just as well with ReadLines()

Trevor Johnson Over a year ago

Worked almost perfectly but is there anyway to keep leading zeroes in my text file. Im assuming that they are being removed because of the !string.isNullorEmpty. Anyway to fix that?

Adrian Tocu Over a year ago

No integer has a 0 at the beginning, when you convert string "0502010" to int, it become: 502010. See this post: stackoverflow.com/questions/6615454/…

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