System.Collections.ArrayList

Added in .NET 1.1
This allows you to work with a set of values as if they were an array and a collection at the same time.

System.Collections.ArrayList myArrayList;

Represents a collection of items whose size can be changed dynamically.

ArrayList vs Array

An arraylist is a combination of an array and a collection.
Imagine that you need to keep track of various objects but you have no idea how many.
It is difficult to use an array for this purpose because you must declare the size of the array at compile time.
This is an aray whose size is dynamically increased as required.

Features

An arraylist has the following functionality:
You can address a value by its index
You can quickly sort and reverse the list
You can search sequentially
You can append elements to the end and insert them in a particular position

Different Data Types

These items can have different data types.

System.Collections.ArrayList myArrayList; 
myArrayList = new System.Collections.ArrayList(); 
myArrayList.Add("string"); 
myArrayList.Add(20); 
myArrayList.Add(false); 
Console.WriteLine(myArrayList[1]);

Do not return null ?

return new System.Collections.ArrayList

Methods

Add	Appends an element after the last element in the collection and returns the index where it was inserted.
AddRange
BinarySearch
Clear	Removes all elements from the collection.
Clone
Contains	Returns TRUE if an element exists in the collection.
CopyTo	Copies the elements from the collection to a new one-dimensional array, starting at the specified index in the array.
FixedSize
GetEnumerator	Returns an enumerator to iterate an ArrayList
GetRange
IndexOf	Returns the index of the element in the collection, or -1 if it cannot be found.
Insert	Inserts an element at the specified index.
InsertRange
LastIndexOf
ReadOnly
Remove	Removes an element from the collection
RemoveAt	Removes an element at the specified index from the collection
RemoveRange
Repeat
Reverse	Reverses the order of the elements
SetRange
Sort	Alphabetically sorts the elements
ToArray	Copies all the elements to a new one-dimensional array
TrimToSize

Properties

Capacity	Property contains the number of elements the srray can currently hold.
Count	Returns the number of elements in the collection.
IsFixedSize	Returns TRUE if no more elements can be added to the collection.
IsReadOnly	Returns TRUE is the elements cannot be altered.

Generic Version

The generic version of this collection is System.Collections.Generic.List