What is Arraylist ?
ArrayList is a non-generic collection of objects whose size increases dynamically.
It is the same as Array except that its size increases dynamically.
An ArrayList can store elements of any data type, including integers, strings, objects, etc.
It’s part of the "System.Collections" namespace .
Example
Create an ArrayList
using System.Collections;
ArrayList arlist = new ArrayList();
// or
var arlist = new ArrayList(); // recommended
Adding Elements in ArrayList
Use the Add () method To add an element in the arraylist
An ArrayList can contain multiple null and duplicate values.
Example
var arlist1 = new ArrayList();
arlist1.Add(1);
arlist1.Add("Bill");
arlist1.Add(" ");
arlist1.Add(true);
arlist1.Add(4.5);
arlist1.Add(null);
Adding elements using object initializer syntax
var arlist2 = new ArrayList()
{
2, "Steve", " ", true, 4.5, null
};
Accessing an ArrayList
The ArrayList class implements the IList interface. So, elements can be accessed using indexer, in the same way as an array. Index starts from zero(0) and increases by one for each subsequent element
Iterate an ArrayList
use the foreach and the for loop to iterate an ArrayList. The Count property of an ArrayList returns the total number of elements in an ArrayList
Remove Elements from ArrayList
Use the Remove(), RemoveAt(), or RemoveRange methods to remove elements from an ArrayList.
Example
arList.Remove(null); //Removes first occurrence of null
arList.RemoveAt(4); //Removes element at index 4
arList.RemoveRange(0, 2);//Removes two elements starting from 1st item (0 index)
Check Element in ArrayList
Use the Contains() method to determine whether the specified element exists in the ArrayList or not.
Get count of element in Arraylist
Gets the number of elements using count() method in the ArrayList