For loop c# only prints the last element of loop in windows form

Question

I am making a Windows Form app in C#. I need to print an array with random numbers on the screen.

There are 20 numbers in total (0 till 19). But it only prints the 19th element. Can anyone help me out? (See image) Don't worry about the comparison number. I just want to print all arrays in the label in the form. Here is some code:

const int numberOfItems = 20;
   
private void Form1_Load(object sender, EventArgs e)
{
    CultureInfo ci = new CultureInfo("en-US");
    Thread.CurrentThread.CurrentUICulture = ci;
    Thread.CurrentThread.CurrentCulture = ci;

    int[] numbers = new int[numberOfItems];

    Random random = new Random();
    double total = 0;
          
    for (int i = 0; i < numbers.Length; i++)
    {
        numbers[i] = random.Next(501);  
        beforeLoop.Text = $"Element {i} = {numbers[i]}";
        total += numbers[i];
    }
}

private void compare_Click(object sender, EventArgs e)
{
    int[] numbers = new int[numberOfItems];

    Random random = new Random();
    double total = 0;
    for (int i = 0; i < numbers.Length; i++)
    {
        numbers[i] = random.Next(501);
              
        int numberBigger = numbers[i] + 10;
        int numberSmaller = numbers[i] - 5;
        total += numbers[i];
        int number = int.Parse(numberBox.Text);

        if (number > numbers[i])
        {
            printLabel.Text = $"Element {i} = {numberBigger}";
        }
        else
        {
            printLabel.Text = $"Element {i} = {numberSmaller}";
        }
    }
}

You repeatedly assign values to beforeLoop.Text. Since your computer is probably quite fast, shouldn't it be obvious that you will only see the result of the final assignment? — Timbo
– Timbo, Commented Oct 6, 2022 at 15:30
You're currently reassigning the Text Property which is overwriting any previously set values. Try using "+=" instead of just "=" and see if that works. You may also need a "new line" character (try System.Environment.NewLine) at the end to put each "Element" on its own line. — user959631
– user959631, Commented Oct 6, 2022 at 15:34
For future questions please re-read minimal reproducible example guidance on posting code. There is really no need to all "generate random" part, or whole compare_Click method. Ideally even removing for loop and replacing it with two assignments like string s = "a"; s = "b"; and question like "where 'a' goes after the second assignment". — Alexei Levenkov
– Alexei Levenkov, Commented Oct 6, 2022 at 15:43
You are just assigning one value at a time to the textbox wuth beforeLoop.Text = $"Element {i} = {numbers[i]}";. Did you want to use a multiline textbox, or a listbox or some other control to display multiple lines of text. — John Alexiou
– John Alexiou, Commented Oct 6, 2022 at 16:40

Said Al Souti · Accepted Answer · 2022-10-06 15:37:18Z

From your question, I understand that you want to concatenate the strings and print them in multiline label control. If so, then try this code:

const int numberOfItems = 20;

private void Form1_Load(object sender, EventArgs e)
{
    CultureInfo ci = new CultureInfo("en-US");
    Thread.CurrentThread.CurrentUICulture = ci;
    Thread.CurrentThread.CurrentCulture = ci;

    int[] numbers = new int[numberOfItems];

    Random random = new Random();
    double total = 0;
   
    var text = "";
    for (int i = 0; i < numbers.Length; i++)
    {
        numbers[i] = random.Next(501);
        
        text += $"Element {i} = {numbers[i]} \n";
        total += numbers[i];
    }

    beforeLoop.Text = text;
}

private void compare_Click(object sender, EventArgs e)
{


    int[] numbers = new int[numberOfItems];

    Random random = new Random();
    double total = 0;
    var text = "";
    for (int i = 0; i < numbers.Length; i++)
    {
        numbers[i] = random.Next(501);
        
        int numberBigger = numbers[i] + 10;
        int numberSmaller = numbers[i] - 5;
        total += numbers[i];
        int number = int.Parse(numberBox.Text);

        if (number > numbers[i])
        {
            text += $"Element {i} = {numberBigger} \n";
        }
        else
        {
            text +=  $"Element {i} = {numberSmaller} \n";
        }
        printLabel.Text = text;
    }
}

The solution here is to add text to a variable in each loop combined by a new line \n. Another solution is to append the text to a c# list. Then join the list with a new line to get a multi-lines string.

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