How to sum a value with string on listbox?

Question

I just want to know how to get the total value.

here's an example inside the listbox:

Soda - 30
Food - 50

How can I sum the 30 and 50 and show it on a textbox? Please help. My code for adding to listbox is:

listBox1.Items.Add("btnSoda.text");

and my code for button that will get the total value:

int i = 0, result = 0;
while (i < listBox1.Items.Count)
{           
    result += Convert.ToInt32(listBox1.Items[i++]);
}

textboxtotal.Text = Convert.ToString((double)result)

after I run the program and click on getTotal Value it shows an error:

An unhandled exception of type 'System.FormatException' occurred in mscorlib.dll

Create an Item class which has two properties, for example: ItemName, and ItemPrice, and after that you can iterate through the listbox items and sum the price values. — IamK
– IamK, Commented Aug 1, 2017 at 11:57
Check this. You have to create key value pair. Then you can add the same by using values. — Lifewithsun
– Lifewithsun, Commented Aug 1, 2017 at 11:58
can you give me an example in code form? im sorry im just a newbie who is willing to learn. Thank you very much :) @C1sc0 — Mark
– Mark, Commented Aug 1, 2017 at 11:58
@Lifewithsun KeyValue pair is a bad choice. Use a own class instead (see C1sc0) because it's the cleaner way and better to read. — Mighty Badaboom
– Mighty Badaboom, Commented Aug 1, 2017 at 11:59

Mighty Badaboom · Accepted Answer · 2017-08-01 12:25:55Z

I would recommend using an own class for your items. Something like

public class Item
{
    public string Name { get; set; }
    public int Price { get; set; }

    public Item(string name, int price)
    {
        Name = name;
        Price = price;
    }
}

Instead of

listBox1.Items.Add("btnSoda.text");

you have to write

List<string> lines = File.ReadAllLines("btnSoda.text");
List<Item> items = new List<Item>();

foreach(string line in lines)
{
    string[] parts = line.Split(new string[] { "-" }, StringSplitOptions.RemoveEmptyEntries);
    string name = parts[0];
    int price = int.Parse(parts[1]);
    Item item = new Item(name, price);
    items.Add(item);
}

comboBox1.DataSource = items;

With this piece of code you are reading your file and creating the Item items you want to show in your ComboBox. The advantage is that you have specific items with the properties you need and not a string which you have to interpret each time you want to do something with it.

Don't forget to set the DisplayMember property too name of your combobox. Otherwise you would not see the names of the items in your ComboBox.

After that you can use

int sum = comboBox1.Items
                   .OfType<Item>()
                   .Sum(x => x.Price);

label1.Text = sum.ToString();

to sum the prices.

Maybe it seems a bit more complicated then the other answer but it's the cleaner way.

Some advantages

you will find out about errors in your textfile when you init your ComboBox and not when calculating the sum
you don't have to interpret your items each time you want to do something with 'em because you already did that at the start
easier to understand and read: no magic strings or numbers

Roman · Accepted Answer · 2017-08-01 12:20:49Z

1

You can use Split() and Sum():

var sum = listBox1.Items
         .OfType<string>()
         .Select(s => Convert.ToInt32(s.Split(new string[] { "-" }, StringSplitOptions.RemoveEmptyEntries)[1]))
         .Sum();

and then:

lbltotal.Text = sum.ToString();

Also, you can change your code a little and it should work:

while (i < listBox1.Items.Count)
{           
    result += Convert.ToInt32(((string)listBox1.Items[i++]).Split(new string[] { "-" }, StringSplitOptions.RemoveEmptyEntries)[1]);
}

edited Aug 1, 2017 at 12:20

answered Aug 1, 2017 at 11:59

Roman

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4 Comments

sujith karivelil Over a year ago

If he is a beginner, definitely he will get confused with this piece of code, But nice and quick, I hope you should take the first index instead for second, that means s.Split(..)[2] should be s.Split(..)[1]

Mark Over a year ago

can i ask where will i put this codes? thank you for answering :)

Roman Over a year ago

@Mark, simply replace your code with whileloop by this

Mark Over a year ago

@RomaDoskoch thank you very much it works! i've accept your answer! Thank you again :)

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