I need to find the average of the grades that are entered in the listbox PLEASE HELP!

Question

1.00/5 (2 votes)

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C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace FindAverage
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        int grade, average;

        private void button2_Click(object sender, EventArgs e)
        {
            grade = Int32.Parse(textBox1.Text);

            LstGrades.Items.Add(grade);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            average = LstGrades.Items. / LstGrades.Items.Count;
        }
    }
}

Posted 18-Nov-14 4:20am

Member 11190214

Updated 18-Nov-14 4:43am

Nelek

v2

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Comments

ZurdoDev 18-Nov-14 10:29am

What is your question?

Nelek 18-Nov-14 10:44am

How to make the average of the grades entered in listbox? ;P

ZurdoDev 18-Nov-14 10:54am

See Solution 1. This is very basic. Just loop through the item and add them up and then divide by the count.

It may help you to write out pseudo code, meaning you write it out in short english sentences and then translate that into code.

Nelek 18-Nov-14 10:56am

You didn't realize it was me, with a irony smily at the end, did you?

ZurdoDev 18-Nov-14 10:57am

Oops. Nope, I did not.

[blushing/]

4 solutions

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OriginalGriff · Accepted Answer · 2014-11-18T04:35:00

Solution 1

There are a couple of ways to do this, but the simplest is just to use a foreach loop:

C#

int total = 0;
foreach (object o in LstGrades.Items)
   {
   total += (int) o;
   }

And then divide by the count to get the average.

Posted 18-Nov-14 4:35am

OriginalGriff

Comments

Manas Bhardwaj 18-Nov-14 10:44am

Yes +5!

DamithSL · Accepted Answer · 2014-11-18T04:36:00

Solution 2

You can use LINQ

C#

var sum = LstGrades.Items.Cast<int>().Sum();
average = sum / LstGrades.Items.Count;

or simple loop

C#

int sum = 0;
foreach (var item in LstGrades.Items)
{
    int result;
    if(int.TryParse(item.ToString(), out result))
            sum += result;
}
average = sum / LstGrades.Items.Count;

Posted 18-Nov-14 4:36am

DamithSL

Updated 18-Nov-14 4:50am

v4

Comments

Manas Bhardwaj 18-Nov-14 10:44am

Ditto +5!

DamithSL 18-Nov-14 10:56am

:)

BillWoodruff 18-Nov-14 11:31am

Post redacted because it reflected an incorrect assumption on my part about the solution given.

DamithSL 18-Nov-14 11:59am

I haven't received any errors from my code, what is the error you get?

BillWoodruff 18-Nov-14 12:55pm

Let me ask how you have created the ListBox Items. If you inserted integer values into the ListBox in code, then, yes, your first example will work.

Since the OP appears to be inserting integer values into the ListBox.Items, I think I should change my vote to #4 !

The potential problem I see is your using Cast to 'int because ListBox Items are by default ... if entered as Type 'string in the design-time editor ... Type 'object. You could, however, Cast to 'string, or 'object, and then the Linq will not break.

But, if you are going to use Linq, why not also use the 'Average function of Enumerable ?

DamithSL 18-Nov-14 13:05pm

It is clear that OP enter only the integers, there is no point on casting to string and then convert to integer.
Agreed with last point, Since you have that part in your answer I don't need to update mine.

BillWoodruff 18-Nov-14 13:19pm

Fair enough. I am changing my vote to a #5.

Manas Bhardwaj · Accepted Answer · 2014-11-18T04:38:00

Solution 3

What about this?

C#

var sum = 0;

for(var count = 0; count < LstGrades.Items.Count; count++)
{
    sum += int.Parse(LstGrades.Items[count].ToString());
}

var average = sum / LstGrades.Items.Count;

Posted 18-Nov-14 4:38am

Manas Bhardwaj

Updated 18-Nov-14 4:57am

v3

Comments

Manas Bhardwaj 18-Nov-14 10:49am

Dear Platinum Downvoter, considering that you have been here for long, wouldn't it be nice that you put a note for your downvote.

Your comment would really help to improve and see what's wrong.

DamithSL 18-Nov-14 10:55am

I think int.parse is wrong :) it should be int.Parse, C# is case sensitive
5wd! ( I assume you will correct it)

Manas Bhardwaj 18-Nov-14 10:57am

Thanks for noticing. Corrected!

BillWoodruff 18-Nov-14 11:32am

Vote of #5 to counteract an unwarranted down-vote. Even if the vote was based on a spelling error, I don't think a down-vote was appropriate.

BillWoodruff · Accepted Answer · 2014-11-18T05:28:00

Solution 4

C#

// requires Linq

private double average;

private void btnGetAverage_Click(object sender, EventArgs e)
{
    average = lstGrades.Items
        .OfType<object>()
            .Select(o => Convert.ToInt32(o))
                .Average();
}

Posted 18-Nov-14 5:28am

BillWoodruff