C# ArrayList Class
The System.Collection.ArrayList class is similar to arrays, but can store elements of any data type. It is collection that can be declared with or without specifies its size. The size of the ArrayList can grow dynamically as the number of elements increases. ArrayList can be accessed using foreach or for loop or indexer.
ArrayList list = new ArrayList(); //declaration without size (dynamic) Or ArrayList list = new ArrayList(20); //declaration with size
C# ArrayList - Methods
Add elements - ArrayList
Adds an element at the end of an ArrayList.
Example 1: Add elements in ArrayList and display it.
static void Main()
{
ArrayList list = new ArrayList();
list.Add(10);
list.Add(20);
list.Add("String value");
list.Add(40.5);
foreach(var item in list)
{
Console.WriteLine(item);
}
}
20
String value
40.5
Insert elements - ArrayList
Use the Insert() method to insert a single item at the specified index.
Example 2: Insert element in arraylist
ArrayList list = new ArrayList();
list.Add(10);
list.Add("Two");
list.Add(30);
list.Insert(1, "Second Item");
list.Insert(2, 100);
foreach (var item in list)
Console.WriteLine(item);
Second Item
100
30
Remove elements - ArrayList
Use the Remove() method to remove a specified element from an ArrayList.
Example 3: Remove element from an arraylist
ArrayList list = new ArrayList();
list.Add(10);
list.Add(20);
list.Add(30);
list.Add(40);
list.Remove(20);
foreach (var item in list)
Console.WriteLine(item);
30
40
Sort elements - ArrayList
Sort() method arrange elements in ascending order. However, all the elements should have same data type otherwise it will throw runtime exception.
Example 4: Sort elements from an arraylist
ArrayList list = new ArrayList();
list.Add(10);
list.Add(5);
list.Add(20);
list.Add(15);
list.Sort();
Console.WriteLine("Ascending Order:");
foreach(var item in list)
Console.WriteLine(item);
10
15
20
Reverse elements - ArrayList
Reverse() method arrange elements in reverse order according to the index of the ArrayList, value in the 0th index appears in last.
Example 5: Reverse elements from an arraylist
ArrayList list = new ArrayList();
list.Add(10);
list.Add(5);
list.Add(20);
list.Add(15);
list.Reverse();
Console.WriteLine("Reverse Order:");
foreach(var item in list)
Console.WriteLine(item);
20
5
10
Contains() method - ArrayList
Contains checks whether specified element exists in the ArrayList or not. Returns true if exists otherwise false.
Example 6: Check existing element in arraylist
ArrayList list = new ArrayList(); list.Add(10); list.Add(20); list.Add(30); Console.WriteLine(list.Contains(10)); Console.WriteLine(list.Contains(50));
false
Difference between Array and ArrayList
Exercise Question: ArrayList
- Input n numbers and add in arraylist.
