Add to array list from another array list

Question

I have a program where I am trying to move items from one arraylist to another via a listbox but when I try to add it to the the second arraylist it does not add there.

ArrayList list1 = new ArrayList();
ArrayList list2 = new ArrayList();
list1.Add(new Class(var1, var2, var3, var4, var5, var6, var7));
foreach (object o in list1)
        {
            class m = (class)o;
            selectionBox.Items.Add(m);
        }

I initialised everything above and added everything to the class and then to the listbox. Note the vars I have got from an XML file.

 bool req = true;

        if (selectionBox.SelectedItem != null)
        {
            Count++;
            errorLabel.Text = "";

            for (int i = 0; i < selectionBox.Items.Count; i++)
            {
                if (selectionBox.GetSelected(i) == true)
                {

                    class m = selectionBox.SelectedItem as class;
                    if (m.var2 == ((Modules)selectionBox.Items[i]).var2)
                    {
                        list2.Add(list1.IndexOf(i));
                    }
                }
            }

        }
        else
        {
            errorLabel.Text = "Error";
        }

Here I am trying to add it to the second array list but it does not work the if statement however is correct I have tried this with print statements. So can someone tell me why the following line does not add to the list?

 list2.Add(list1.IndexOf(i));

It's hard to understand what you are going to do. Can you make it more clear? e.g. What is the use of Count variable? — Hossein Narimani Rad
– Hossein Narimani Rad, Commented Mar 25, 2013 at 13:35
Right I am not sure what has confused you but I will try again, what I am trying to do is read from an xml file and add the values inside tags to variables, I then add those variables to an array list and a listbox. When I move items from one listbox to another I want to move all the vars related with it to the second array list, I hope this clears things up. — user2157179
– user2157179, Commented Mar 25, 2013 at 13:41

Davin Tryon · Accepted Answer · 2013-03-25 13:43:31Z

1

list2.Add(list1.IndexOf(i)); will give you the index (position) of each element. Not the element itself.

To add the element you would need to do something like this:

list2.Add(list1[i]);

Also, just as an aside, this will only copy the reference to each element, it will not create a new copy of each.

answered Mar 25, 2013 at 13:43

Davin Tryon

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1 Comment

user2157179 Over a year ago

@David Tyron Thanks this has worked for me but it seems to have a bug in when I try to write it to an XML I seem to often get the first tag appearing many times instead of 8 different tags as each variable is different.

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