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C# ArrayList Class: Dynamic Array

In this tutorial, we'll demonstrate how to use the ArrayList class in C#. The ArrayList class is a dynamic array, which means that its size can be changed during runtime. It is part of the System.Collections namespace.

Set up the environment

Create a new C# Console Application project in Visual Studio and add the following namespace:

using System.Collections;

Create an ArrayList

Create an instance of the ArrayList class:

ArrayList myArrayList = new ArrayList();

Add elements to the ArrayList

You can use the Add method to add elements to the ArrayList:

myArrayList.Add(10);
myArrayList.Add("Hello");
myArrayList.Add(3.14);

Note that the ArrayList can store different types of elements, unlike an array.

Access elements in the ArrayList

To access elements in the ArrayList, use the indexer property and provide the index:

int firstElement = (int)myArrayList[0];
string secondElement = (string)myArrayList[1];

Note that you need to cast the elements to their appropriate types since the ArrayList stores elements as objects.

Insert and remove elements in the ArrayList

Use the Insert method to insert an element at a specified index:

myArrayList.Insert(1, "World");

Use the Remove method to remove the first occurrence of an element:

myArrayList.Remove(3.14);

Use the RemoveAt method to remove an element at a specified index:

myArrayList.RemoveAt(2);

Loop through the ArrayList

Use a foreach loop to iterate through the elements of the ArrayList:

foreach (object item in myArrayList)
{
    Console.WriteLine($"Element: {item}");
}

ArrayList properties and methods

The ArrayList class has several useful properties and methods, such as Count, Contains(), and IndexOf(). For example:

int count = myArrayList.Count; // Returns the number of elements in the ArrayList
bool contains = myArrayList.Contains("Hello"); // Returns true if the ArrayList contains the specified element
int index = myArrayList.IndexOf("Hello"); // Returns the index of the first occurrence of the specified element in the ArrayList

In this tutorial, we've shown you how to use the ArrayList class in C#. The ArrayList class is a dynamic array that can store elements of different types and resize itself during runtime. However, it is worth noting that the ArrayList class is not type-safe and has some performance overhead due to boxing and unboxing of value types. In most cases, it is recommended to use the generic List<T> class from the System.Collections.Generic namespace, which provides type safety and better performance.

C# ArrayList example:

Description: This example introduces the ArrayList class in C#, demonstrating its use as a dynamic array that can store elements of different types.

Code:

// Create and initialize an ArrayList
ArrayList arrayList = new ArrayList();
arrayList.Add(1);
arrayList.Add("Hello");
arrayList.Add(3.14);

// Access and print elements of the ArrayList
foreach (var element in arrayList)
{
    Console.WriteLine(element);
}

How to declare and initialize ArrayList in C#:
- Description: This example guides you through the process of declaring and initializing an ArrayList in C#.
- Code:
```
// Declare and initialize an ArrayList
ArrayList arrayList = new ArrayList();
arrayList.Add(1);
arrayList.Add(2);
arrayList.Add(3);
```

Accessing elements in an ArrayList in C#:

Description: Demonstrating how to access individual elements in an ArrayList using index notation.

Code:

ArrayList arrayList = new ArrayList();
arrayList.Add("Apple");
arrayList.Add("Banana");

// Access and print specific elements
Console.WriteLine(arrayList[0]); // Output: Apple
Console.WriteLine(arrayList[1]); // Output: Banana

Iterating through an ArrayList in C#:

Description: Showcasing different methods for iterating through an ArrayList in C#, such as using foreach and traditional for loops.

Code:

ArrayList arrayList = new ArrayList();
arrayList.Add(1);
arrayList.Add(2);
arrayList.Add(3);

// Using foreach loop
foreach (var element in arrayList)
{
    Console.WriteLine(element);
}

// Using for loop
for (int i = 0; i < arrayList.Count; i++)
{
    Console.WriteLine(arrayList[i]);
}

Adding and removing elements from ArrayList in C#:

Description: This example demonstrates how to add and remove elements dynamically from an ArrayList in C#.

Code:

ArrayList arrayList = new ArrayList();
arrayList.Add(1);
arrayList.Add(2);
arrayList.Add(3);

// Add a new element
arrayList.Add(4);

// Remove an element
arrayList.Remove(2);

Sorting an ArrayList in C#:

Description: Illustrating how to sort an ArrayList in ascending order using the ArrayList.Sort method.

Code:

ArrayList arrayList = new ArrayList();
arrayList.Add(5);
arrayList.Add(3);
arrayList.Add(1);

// Sort the ArrayList in ascending order
arrayList.Sort();

// Print the sorted ArrayList
foreach (var element in arrayList)
{
    Console.WriteLine(element);
}

Searching for an element in an ArrayList C#:

Description: Introducing methods for searching for an element in an ArrayList, such as using ArrayList.IndexOf.

Code:

ArrayList arrayList = new ArrayList();
arrayList.Add("Apple");
arrayList.Add("Banana");
arrayList.Add("Orange");

// Find the index of the target element
int index = arrayList.IndexOf("Banana");

// Print the index or a message if not found
Console.WriteLine(index != -1 ? $"Element found at index {index}" : "Element not found");

Passing ArrayList as parameters in C#:

Description: This example demonstrates how to pass ArrayList as parameters to methods in C#, enabling modular and reusable code.

Code:

// Method that takes an ArrayList as a parameter
static void PrintArrayList(ArrayList list)
{
    foreach (var element in list)
    {
        Console.WriteLine(element);
    }
}

// Declare and initialize an ArrayList
ArrayList arrayList = new ArrayList();
arrayList.Add(1);
arrayList.Add(2);
arrayList.Add(3);

// Invoke the method with the ArrayList as a parameter
PrintArrayList(arrayList);