ArrayList Methods in C#

The ArrayList class in C# is a part of the System.Collections namespace and offers a flexible array structure that can grow and shrink dynamically. Unlike standard arrays, ArrayList can hold elements of any type and provides a variety of methods to perform different operations such as adding, removing, sorting, and searching items. This article will explore some of the key methods provided by the ArrayList class and demonstrate how to use them effectively.

Understanding ArrayList

ArrayList is a dynamic array for storing and manipulating a list of objects. It stores elements as objects, which means any type of data (value or reference type) can be added to the collection. This flexibility comes at the cost of performance due to boxing and unboxing operations for value types.

Key Methods of ArrayList

Here are some of the fundamental methods provided by the ArrayList class:

Add(Object): Adds an element to the end of the ArrayList.

Remove(Object): Removes the first occurrence of a specific object from the ArrayList.

Insert(Int32, Object): Inserts an element into the ArrayList at the specified index.

RemoveAt(Int32): Removes the element at the specified index.

Clear(): Removes all elements from the ArrayList.

Sort(): Sorts the elements in the entire ArrayList.

BinarySearch(Object): Searches the entire sorted ArrayList for an element using a binary search algorithm and returns the zero-based index of the element.

Contains(Object): Determines whether an element is in the ArrayList.

CopyTo(Array): Copies the entire ArrayList to a compatible one-dimensional array, starting at the beginning of the target array.

Example Usage of ArrayList Methods

ArrayList list = new ArrayList();
list.Add("Apple");
list.Add("Banana");
list.Add("Cherry");

// Removing an item
list.Remove("Banana");

// Inserting a new item
list.Insert(1, "Orange");

// Checking for an item
if (list.Contains("Cherry")) {
    Console.WriteLine("Cherry is in the list.");
}

// Displaying sorted list
list.Sort();
foreach (var item in list) {
    Console.WriteLine(item);
}

Conclusion

ArrayList provides a robust set of methods that make it versatile for handling collections of objects dynamically in C#. However, for better type safety and performance, consider using generic collections like List<T> in new development.

object[] array = new object[myArrayList.Count];
myArrayList.CopyTo(array);

bool contains = myArrayList.Contains(123); // Checks if 123 is in the ArrayList

int index = numbers.BinarySearch(3); // Searches for '3' in the sorted ArrayList

ArrayList numbers = new ArrayList() { 1, 3, 5, 2, 4 };
numbers.Sort(); // Sorts the numbers in ascending order

myArrayList.Clear(); // Empties the entire ArrayList

myArrayList.RemoveAt(0); // Removes the first element

myArrayList.Insert(0, "First"); // Inserts "First" at the beginning of the ArrayList

myArrayList.Remove("Hello"); // Removes "Hello" from the ArrayList

ArrayList myArrayList = new ArrayList();
myArrayList.Add("Hello");
myArrayList.Add(123);