How to delete an element from Arraylist in C#

Question

Lets say I have this loop and I put the data in an ArrayList:

int Num1 = Int32.Parse(textBox1.Text);
int Num2 = Int32.Parse(textBox2.Text);
ArrayList ItemList = new ArrayList();
while (Num1 <= Num2)
{
    ItemList.Add(Num1);
    Num1++;
}

And I have another loop to read my Arraylist:

foreach (int item in ItemList)
{
    listBox1.Items.Add("Number " + item.ToString() + ",");
}

Which gives this result:

Number 1,
Number 2,
Number 3,
Number 4,

I need to remove the last comma in the last item and get this result:

Number 1,
Number 2,
Number 3,
Number 4

I've tried this:

foreach (int item in ItemList)
{
    listBox1.Items.Add("Number " + item.ToString().Trim(',') + ",");
}

But it doesn't work. Can someone please tell me what I did wrong, and how I can fix it?

That's a bit confusing. This is not really about deleting an element from an array, right? — JensG
– JensG, Commented Apr 23, 2015 at 19:20

Josh L. · Accepted Answer · 2015-04-23 20:10:05Z

6

See if this works for your purposes:

var result = string.Join("," + Environment.NewLine, itemList.ToArray());

Forgot the "Number" part:

var result = string.Join(", " + Environment.NewLine, itemList.ToArray().Select(x => "Number " + x));

edited Apr 23, 2015 at 20:10

answered Apr 23, 2015 at 19:12

Josh L.

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9 Comments

JensG Over a year ago

I was about proposing the same. Neat, clean, simple.

Padraic Over a year ago

Of course, instead of adding integers 1, 2, 3... you would need to a "Number 1", "Number 2", "Number 3" .... to your ArrayList instead.

Guffa Over a year ago

That will use the String.Join(string, params object[]) overload, so the result is "System.Collections.ArrayList".

Padraic Over a year ago

Yeah either call itemList.ToArray() or just use a List<string> instead of the ArrayList

user2460074 Over a year ago

@JoshL. Thanks a Lot for help and sorry if i waste your time

|

Dom · Accepted Answer · 2015-04-23 20:01:18Z

3

listBox1.Items.Add("Number " + item.ToString() + 
ItemList.IndexOf(item) == ItemList.Count - 1 ? string.Empty : ",");

edited Apr 23, 2015 at 20:01

answered Apr 23, 2015 at 19:10

Dom

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2 Comments

JensG Over a year ago

What's the complexity of IndexOf() again? Was it O(N) maybe? And what if we are doing this in a loop?

user2460074 Over a year ago

thanks but it dosn't work i have a red line this part ItemList.Count()

paulofer85 · Accepted Answer · 2015-04-23 19:18:13Z

0

you should not modify the item of your collection inside a foreach.

May be you should try to modify your collection ItemList before the foreach that shows your result .

You can make somthing like this (before the foreach that shows your results):

ItemList[ItemList.Length-1] = ItemList[ItemList.Length-1].SubString(0,ItemList.Length -2);

answered Apr 23, 2015 at 19:18

paulofer85

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Comments

Winky2222 · Accepted Answer · 2015-04-23 20:15:03Z

0

How about this:

foreach (int item in ItemList)
{
    if (listBoxOne.Items == null)
    {
        listBox1.Items.Add("Number " + item.ToString());
    }
    else
    {
        listBox1.Items.Add(",\n" + "Number " + item.ToString());
    }

    //Or more simply below
    listBoxOne.Items.Add = listBoxOne.Items == null ? ("Number " + item.ToString()) : (",\n" + "Number " + item.ToString());

answered Apr 23, 2015 at 20:15

Winky2222

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