C# Array List

In this C# tutorial chapter, we will learn about Array List in C#. In C#, ArrayList is a non-generic collection, it is useful to store data of various data-type, one of the main advantage of using ArrayList is, size of ArrayList can grow and shrink dynamically. The ArrayList class is defined in the System.Collections namespace.

What is ArrayList in C#?

As explained above ArrayList in C#, is basically a non-generic collection, that works like an array but provides the facilities such as dynamic resizing, adding and deleting elements from the collection, unlike array where we specify array size and cannot add elements more than specified size.

• To use an ArrayList you need to add a System.Collections namespace.
• ArrayList implements the System.Collections.IList interface using an array whose size is dynamically increased as required.
• ArrayList collection accepts null as a valid value, an allows duplicate elements.
• ArrayList cannot store multi-dimensional array.
• It can have any number of elements, as item in ArrayList can be added or deleted dynamically.

ArrayList Declaration

Here is how to declare arraylist in C#

ArrayList arrayList = new ArrayList();

In the above code, we have declared arrayList as ArrayList, with an instance of arraylist class without specifying any size.

Useful ArrayList Methods and Properties

Although there are many methods, properties of ArraList in C#, I have mentioned few but mostly used methods and properties.

• Add: Adds an object to the end of the ArrayList.
• Clear: Removes all elements from the ArrayList.
• Contains: Determines whether an element is in the ArrayList.
• GetRange: Returns an ArrayList which represents a subset of the elements in the source ArrayList.
• IndexOf: Returns the zero-based index of the first occurrence of a value in the ArrayList or in a portion of it.
• Insert: Inserts an element into the ArrayList at the specified index.
• Remove: Removes the first occurrence of a specific object from the ArrayList.
• Count: Gets the number of elements actually contained in the ArrayList.
• IsFixedSize: Gets a value indicating whether the ArrayList has a fixed size.
• IsSynchronized: It is used to get a value to indicate that access to arraylist is synchronized (thread-safe) or not.

ArrayList Example

using System;
using System.Collections;
					
public class CsharpArrayListProgram
{
	public static void Main()
	{
		ArrayList arrayList = new ArrayList();  
	     // add elements in ArrayList
        arrayList.Add("C#");
        arrayList.Add("ASP.Net");         
        arrayList.Add("SQL");
		   
		//print initial arrayList 
		Console.WriteLine("Initial ArrayList:");
		ShowArrayList(arrayList);
		
		//remove element from arrayList
		arrayList.RemoveAt(1); //remove element using Index
		
		//print arrayList after deletion
		Console.WriteLine("ArrayList After deletion:");
		ShowArrayList(arrayList);
		
		//Gets the number of elements actually contained in the ArrayList.
		Console.WriteLine("Item count of arrayList: "+ arrayList.Count);
		
		//Check if Element exists using .Contains
		Console.WriteLine("Item 'C#' Exists in ArrayiList: "+ arrayList.Contains("C#"));
	}
	
	//print ArrayList item using foreach
	public static void ShowArrayList(ArrayList list)
	{
		foreach(var item in list)
		{
			Console.WriteLine(item);
		}
	}
}

Output:

Initial ArrayList:
C#
ASP.Net
SQL
ArrayList After deletion:
C#
SQL
Item count of arrayList: 2
Item 'C#' Exists in ArrayiList: True

In the above program, we are initializing arrayList and then adding few elements.

We are printing values of ArrayList using foreach loop, we are also using various methods and properties in the above C# program.