Adding new items to an arraylist

[Extremest]

Is there a way to add new items to an arraylist witht he indexer? like
with a normal array I can just do like array[x] = new. What I have
read with arraylist it will throw an exception if I try to do this. Or
is there a way to find out how many things are actually in an array
without it counting the null sections? Say I have an array[10] but
only have 5 things in there how can I easily find out that there are 5?

[Barry Kelly]

"Extremest" <dn**********@c harter.net> wrote:

Is there a way to add new items to an arraylist witht he indexer? like
with a normal array I can just do like array[x] = new. What I have
read with arraylist it will throw an exception if I try to do this.
Are you working with the ArrayList class? If so, the following code
works fine for me, with no exceptions thrown:

---8<---
using System;
using System.Collecti ons;

class App
{
static void Main()
{
ArrayList list = new ArrayList();
list.Add(null);
list.Add(null);

list[0] = new App();
list[1] = new App();
}
}
--->8---

Are you doing something different?
Or
is there a way to find out how many things are actually in an array
without it counting the null sections? Say I have an array[10] but
only have 5 things in there how can I easily find out that there are 5?

It isn't clear whether you're talking about an array or an ArrayList. To
count the number of non-null items in *either* an array *or* an
ArrayList, then you need to iterate through the list and compare with
null - i.e. do the counting yourself:

---8<---
int count = 0;
foreach (object o in a)
if (a != null)
++count;
--->8---

-- Barry

--
http://barrkel.blogspot.com/

[Extremest]

I mean if oyu don't do the add part first and just want to add
something with a specific index number? I didn't know if there was a
way to see how many where in a normal array without doing the loop. I
don't want them to be counted if they are null though. That is what I
meant on the second part.

[Jon Skeet [C# MVP]]

Extremest <dn**********@c harter.net> wrote:

I mean if oyu don't do the add part first and just want to add
something with a specific index number? I didn't know if there was a
way to see how many where in a normal array without doing the loop. I
don't want them to be counted if they are null though. That is what I
meant on the second part.

No, you can't add elements with the indexer.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[Mihaly]

Why not add the ArrayList element only when you add a non null object?
try to use:

ArrayList arr = new ArrayList();
while (condition)
arr.Add(new object());

or if you want to add an element to a specific location, you can use the
ArrayList.Inser t() methode.

Hope it's help you.
Mihaly

"Extremest" wrote:

Is there a way to add new items to an arraylist witht he indexer? like
with a normal array I can just do like array[x] = new. What I have
read with arraylist it will throw an exception if I try to do this. Or
is there a way to find out how many things are actually in an array
without it counting the null sections? Say I have an array[10] but
only have 5 things in there how can I easily find out that there are 5?

[Barry Kelly]

"Extremest" <dn**********@c harter.net> wrote:

I mean if oyu don't do the add part first and just want to add
something with a specific index number?

Perhaps you should look at the Hashtable class instead. You can add to
instances of that class using the indexer (which is actually the key of
the item to add).

-- Barry

--
http://barrkel.blogspot.com/