ArrayList in ArrayList in C#?

Question

I want to have an ArrayList in an ArrayList. This is how I did it:

ArrayList arraylist1 = new ArrayList();

ArrayList arraylist2 = new ArrayList();
arraylist2.Items.Add("test1");
arraylist2.Items.Add("test2");

arraylist1.Items.Add(arraylist2);

Now how can I call the arraylist?

I tried it this way:

arraylist1[0][0].ToString()
arraylist1[0][1].ToString()

It didn't work. Does anyone have any other ideas?

Thanks.

a) ArrayList is deprecated for List<T>. b) It didn't work is not a helpful error description. — TaW
– TaW, Commented May 28, 2020 at 8:49
As the ArrayList documentation itself says - "We don't recommend that you use the ArrayList class for new development. Instead, we recommend that you use the generic List<T> class. The ArrayList class is designed to hold heterogeneous collections of objects. However, it does not always offer the best performance." — stuartd
– stuartd, Commented May 28, 2020 at 14:43

Risto M · Accepted Answer · 2020-05-28 08:15:40Z

4

This way using Generic List<string> and List<List<string>> types found in System.Collections.Generic-namespace:

var listOfStrings = new List<string>();
listOfStrings.Add("test1");
listOfStrings.Add("test2");

var listOfStringLists = new List<List<string>>();
listOfStringLists.Add(listOfStrings);

Console.WriteLine(listOfStringLists[0][0]);
Console.WriteLine(listOfStringLists[0][1]);

edited May 28, 2020 at 8:15

answered May 28, 2020 at 8:10

Risto M

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Comments

Guru Stron · Accepted Answer · 2020-05-28 08:14:31Z

0

The array list you use just returns objects, so you'd have to cast the outer entry 1st: ((ArrayList)arraylist1[0])[0]

As it was already proposed above, better use the generic List

edited May 28, 2020 at 8:14

Guru Stron

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answered May 28, 2020 at 8:12

Ronald Korze

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