How to sum all numbers in a Listbox using TextBox?

Question

I want to count and sum all values in a ListBox. For example, I have the following values in my ListBox: 4, 6, 1, 7. My current value is 18. If I add a 2 with a TextBox, I need to get 20 and if I add 5 I need to get 25 in total.

If I try it with the below code, it gives me a whole other number.

Here is my code:

private void AddButton_Click(object sender, EventArgs e)
{
    decimal sum;
    listBox2.Items.Add(TextBox1.Text);
    TextBox1.Text = "";

    for (int i = 0; i < listBox2.Items.Count; i++)
    {
        sum += Convert.ToDecimal(listBox2.Items[i].ToString());
    }

    Label1.Text = sum.ToString();
}

What other number does it give you? Can you step with the debugger through the loop and check each value that's getting added up? Small tip: Use a foreach instead of a for loop to iterate over the items — äymm
– äymm, Commented Mar 13, 2019 at 13:19

Prasad Telkikar · Accepted Answer · 2019-03-13 13:34:12Z

2

You missed to initialize default value of sum. Assign sum = 0 before adding values to sum variable

private void AddButton_Click(object sender, EventArgs e)
{
    decimal sum = 0;  //Set sum = 0  by default
    listBox2.Items.Add(TextBox1.Text);
    TextBox1.Text = "";

    for (int i = 0; i < listBox2.Items.Count; i++)
    {
        //To check value of sum after each iteration, you can print it on console
        Console.WriteLine("Sum =" +sum);
        sum += Convert.ToDecimal(listBox2.Items[i].ToString());
    }

    Label1.Text = sum.ToString();
}

edited Mar 13, 2019 at 13:34

answered Mar 13, 2019 at 13:21

Prasad Telkikar

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2 Comments

Agiil Over a year ago

Nope i tried it if i had the following numbers 4,5 and 6 it shows as result 28

Prasad Telkikar Over a year ago

Debug your code and check value of sum. Console.WriteLine will definitely helpful here.

NoImagination · Accepted Answer · 2019-03-13 13:32:08Z

1

Sorry for maybe not answer but it is strange that your compiler didn't tell you to initialize sum. The second I tested your code and it works correctly as expected that means that if the problem is not in sum variable then you made something else to this fields somewhere else so your code doesn't work correctly.

Having in mind your comment to previous person I'd say the same. In some cases (I know it's funny but) you may have viruses on your computer. Check it. Once in my life I've failed my maths lab work because of virus that interrupted my program so it drew the wrong chart !sick I know :D

edited Mar 13, 2019 at 13:32

answered Mar 13, 2019 at 13:27

NoImagination

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2 Comments

Prasad Telkikar Over a year ago

agreed with your first para but not with second para. Only because of default initialization code was giving weird results. still +1 for first para...

NoImagination Over a year ago

@PrasadTelkikar man said he tried initialized and still had the problem xD

JohnnBlade · Accepted Answer · 2019-03-13 13:25:54Z

0

    private void button1_Click(object sender, EventArgs e)
    {
        var sum = 0;
        var value = 0;

        listBox1.Items.Add(textBox1.Text);

        foreach (var item in listBox1.Items)
        {
            if (!int.TryParse(item.ToString(), out value))
                continue;

            sum = sum + value;
        }

        label1.Text = sum.ToString();
        textBox1.Text = string.Empty;
    }

answered Mar 13, 2019 at 13:25

JohnnBlade

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Comments

Amit K.S · Accepted Answer · 2019-03-13 13:29:55Z

0

Use of unassigned local variable 'sum', sum must be assigned before use !

decimal sum = 0;

Rest all is ok

answered Mar 13, 2019 at 13:29

Amit K.S

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Comments

Harry · Accepted Answer · 2019-03-13 14:03:02Z

0

Need to set sum to 0 and also it is probably best to use a foreach instead of a Dotloop.

private void AddButton_Click(object sender, EventArgs e) {
    decimal sum = 0;
    listBox2.Items.Add(TextBox1.Text);
    TextBox1.Text = ""; 
    foreach (string s in listBox2) { 
        sum += Convert.ToDecimal(s);
    } 
    Label1.Text = sum.ToString(); 
}

answered Mar 13, 2019 at 14:03

Harry

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1 Comment

Prasad Telkikar Over a year ago

foreach (var s in listBox2.Items) { ... } please correct it.You need to iterate though items not with ListBox. Your code is buggy please correct it

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