Introduction

C# ArrayList is a collection class. This tutorial shows how to use ArrayList in a C# application including Adding ArrayList Items, Removing item from an ArrayList, ArrayList properties, and ArrayList methods.

Create ArrayList

The following code craetes an ArrayList object in C#.

  1. ArrayList arr = new ArrayList();

The datatype of an ArrayList is the object type. We can add any data types such as strings, integers to a collection.

Add ArrayList Items

The Add() method adds items to an ArrayList. The following code adds several items to an ArrayList. The items are of string type. The code also uses a foreach loop that reads all items of the ArrayList and displays on the console.

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList();
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. arr.Add("Tuesday");
  11. arr.Add("Wednesday");
  12. arr.Add("Thusday");
  13. arr.Add("Friday");
  14. arr.Add("Saturday");
  15. Console.WriteLine("The elements of the ArrayList are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. }
  21. }
  22. }

Here is the output.

arraylist_add.jpg

ArrayList Properties

Here is a list of ArrayList properties.

Capacity

Gets or sets the number of elements an ArrayList can store. The default capacity of an ArrayList is 4. If I add 5th element, then the capacity will be doubled (that is 8) relative to the previous one (that is 4).

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList();
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. Console.WriteLine("**********Elements of ArrayList*************");
  11. Console.WriteLine();
  12. foreach (object obj in arr)
  13. {
  14. Console.WriteLine(obj);
  15. }
  16. Console.WriteLine();
  17. Console.WriteLine("Capacity of the ArrayList is:" + arr.Capacity);
  18. Console.WriteLine();
  19. Console.WriteLine("//Adding Three more elements");
  20. Console.WriteLine("**********Elements of ArrayList*************");
  21. Console.WriteLine();
  22. arr.Add("Tuesday");
  23. arr.Add("Wednesday");
  24. arr.Add("Thusday");
  25. foreach (object obj in arr)
  26. {
  27. Console.WriteLine(obj);
  28. }
  29. Console.WriteLine();
  30. Console.WriteLine("Now the Capacity is:" + arr.Capacity);
  31. Console.WriteLine();
  32. Console.WriteLine("//Adding Four more elements");
  33. Console.WriteLine("**********Elements of ArrayList*************");
  34. arr.Add("Friday");
  35. arr.Add("Saturday");
  36. arr.Add("Januray");
  37. arr.Add("Feburay");
  38. foreach (object obj in arr)
  39. {
  40. Console.WriteLine(obj);
  41. }
  42. Console.WriteLine();
  43. Console.WriteLine("Now the Capacity is:" + arr.Capacity);
  44. }
  45. }
  46. }

Here is the output.

arraylist_capacity.jpg

Count

Gets the number of elements actually contained in the ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList();
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. Console.WriteLine("**********Elements of ArrayList*************");
  11. Console.WriteLine();
  12. foreach (object obj in arr)
  13. {
  14. Console.WriteLine(obj);
  15. }
  16. Console.WriteLine();
  17. Console.WriteLine("The number of element in the ArrayList are:" + arr.Count);
  18. Console.WriteLine();
  19. Console.WriteLine("//Adding Three more elements");
  20. Console.WriteLine("**********Elements of ArrayList*************");
  21. Console.WriteLine();
  22. arr.Add("Tuesday");
  23. arr.Add("Wednesday");
  24. arr.Add("Thusday");
  25. foreach (object obj in arr)
  26. {
  27. Console.WriteLine(obj);
  28. }
  29. Console.WriteLine();
  30. Console.WriteLine("Now the number of elements in the ArrayList are:" + arr.Count);
  31. Console.WriteLine();
  32. Console.WriteLine("//Adding Four more elements");
  33. Console.WriteLine("**********Elements of ArrayList*************");
  34. arr.Add("Friday");
  35. arr.Add("Saturday");
  36. arr.Add("Januray");
  37. arr.Add("Feburay");
  38. foreach (object obj in arr)
  39. {
  40. Console.WriteLine(obj);
  41. }
  42. Console.WriteLine();
  43. Console.WriteLine("Now the elements in the ArrayList are:" + arr.Count);
  44. }
  45. }
  46. }

Here is the output.

arraylist_count.jpg

ArrayList Methods


Clear()

Removes all elements from an ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList(7);
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. arr.Add("Tuesday");
  11. arr.Add("Wednesday");
  12. arr.Add("Thusday");
  13. arr.Add("Friday");
  14. arr.Add("Saturday");
  15. Console.WriteLine("The elements in the arraylist are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. Console.WriteLine("The number of element in the arraylist are:" + arr.Count);
  21. arr.Clear();
  22. Console.WriteLine("After apply the clear method the elements in the arraylist are:" + arr.Count);
  23. }
  24. }
  25. }

Here is the output.

arraylist_clear.jpg

Contains()

Determines whether an element is in an ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList(7);
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. arr.Add("Tuesday");
  11. arr.Add("Wednesday");
  12. arr.Add("Thusday");
  13. arr.Add("Friday");
  14. arr.Add("Saturday");
  15. Console.WriteLine("The elements in the arraylist are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. Console.WriteLine();
  21. Console.WriteLine("The element Saturday contain in the arraylist is:" + arr.Contains("Saturday"));
  22. Console.WriteLine("The element Monday contain in the arraylist is:" + arr.Contains("Monday"));
  23. Console.WriteLine("The element Tuesday contain in the arraylist is:" + arr.Contains("Tuesday"));
  24. Console.WriteLine("The element May contain in the arraylist is:" + arr.Contains("May"));
  25. Console.WriteLine("The element Hello contain in the arraylist is:" + arr.Contains("Hello"));
  26. }
  27. }
  28. }

Here is the output.

arraylist_contains.jpg

Insert()

Inserts an element into the ArrayList at the specified index.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList(7);
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. arr.Add("Tuesday");
  11. arr.Add("Wednesday");
  12. arr.Add("Thusday");
  13. arr.Add("Friday");
  14. arr.Add("Saturday");
  15. Console.WriteLine("The elements in the arraylist are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. arr.Insert(0, "********Names of the days*******");
  21. arr.Insert(8, "*********Names of the months**********");
  22. arr.Insert(9, "Janurary");
  23. arr.Insert(10, "Feburary");
  24. arr.Insert(11, "March");
  25. arr.Insert(12, "April");
  26. arr.Insert(13, "May");
  27. Console.WriteLine("The elements in the arraylist are after the insert operation:");
  28. Console.WriteLine();
  29. foreach (object obj in arr)
  30. {
  31. Console.WriteLine(obj);
  32. }
  33. }
  34. }
  35. }

Here is the output.

arraylist_insert.jpg

InsertRange()

Inserts the elements of a collection into the ArrayList at the specified index.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList(7);
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. arr.Add("Tuesday");
  11. arr.Add("Wednesday");
  12. arr.Add("Thusday");
  13. arr.Add("Friday");
  14. arr.Add("Saturday");
  15. Stack stack=new Stack();
  16. stack.Push("Janurary");
  17. stack.Push("Feburary");
  18. stack.Push("March");
  19. stack.Push("April");
  20. stack.Push("May");
  21. stack.Push("June");
  22. stack.Push("July");
  23. stack.Push("August");
  24. stack.Push("September");
  25. stack.Push("October");
  26. stack.Push("November");
  27. stack.Push("December");
  28. Console.WriteLine("The elements in the arraylist are:");
  29. foreach (object obj in arr)
  30. {
  31. Console.WriteLine(obj);
  32. }
  33. arr.Insert(0, "********Names of the days*******");
  34. arr.Insert(8, "*********Names of the months**********");
  35. arr.InsertRange(9, stack);
  36. Console.WriteLine("The elements in the arraylist are after the insert operation:");
  37. Console.WriteLine();
  38. foreach (object obj in arr)
  39. {
  40. Console.WriteLine(obj);
  41. }
  42. }
  43. }
  44. }

Here is the output.

arraylist_insertrange.jpg

IndexOf(object)

Searches for the specified object and returns the zero-based index of the first occurrence within the entire ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList(7);
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. arr.Add("Tuesday");
  11. arr.Add("Wednesday");
  12. arr.Add("Thusday");
  13. arr.Add("Friday");
  14. arr.Add("Saturday");
  15. Console.WriteLine("The elements in the arraylist are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. Console.WriteLine("The index value of Sunday is:" + arr.IndexOf("Sunday"));
  21. Console.WriteLine("The index value of Monday is:" + arr.IndexOf("Monday"));
  22. Console.WriteLine("The index value of Tuesday is:" + arr.IndexOf("Tuesday"));
  23. Console.WriteLine("The index value of Wednesday is:" + arr.IndexOf("Wednesday"));
  24. Console.WriteLine("The index value of Thusday is:" + arr.IndexOf("Thusday"));
  25. Console.WriteLine("The index value of Friday is:" + arr.IndexOf("Friday"));
  26. Console.WriteLine("The index value of Saturday is:" + arr.IndexOf("Saturday"));
  27. }
  28. }
  29. }

Here is the output.

arraylist_indexof.jpg

Remove()

Removes the first occurrence of a specific object from the ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList(7);
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. arr.Add("Tuesday");
  11. arr.Add("Wednesday");
  12. arr.Add("Thusday");
  13. arr.Add("Friday");
  14. arr.Add("Saturday");
  15. Console.WriteLine("The elements in the arraylist are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. arr.Remove("Sunday");
  21. arr.Remove("Monday");
  22. arr.Remove("Tuesday");
  23. Console.WriteLine();
  24. Console.WriteLine("After remove the elements the arraylist is as:");
  25. foreach (object obj in arr)
  26. {
  27. Console.WriteLine(obj);
  28. }
  29. }
  30. }
  31. }

Here is the output.

arraylist_remove.jpg

RemoveAt()

Removes the element at the specified index of the ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  4. class Program
  5. {
  6. static void Main(string[] args)
  7. {
  8. ArrayList arr = new ArrayList(7);
  9. arr.Add("Sunday");
  10. arr.Add("Monday");
  11. arr.Add("Tuesday");
  12. arr.Add("Wednesday");
  13. arr.Add("Thusday");
  14. arr.Add("Friday");
  15. arr.Add("Saturday");
  16. Console.WriteLine("The elements in the arraylist are:");
  17. foreach (object obj in arr)
  18. {
  19. Console.WriteLine(obj);
  20. }
  21. arr.RemoveAt(3);
  22. arr.RemoveAt(1);
  23. arr.RemoveAt(2);
  24. Console.WriteLine();
  25. Console.WriteLine("After remove the elements the arraylist is as:");
  26. foreach (object obj in arr)
  27. {
  28. Console.WriteLine(obj);
  29. }
  30. }
  31. }
  32. }

Here is the output.

arraylist_removeat.jpg

RemoveRange()

Removes a range of elements from the ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList(7);
  8. arr.Add("Sunday");
  9. arr.Add("Monday");
  10. arr.Add("Tuesday");
  11. arr.Add("Wednesday");
  12. arr.Add("Thusday");
  13. arr.Add("Friday");
  14. arr.Add("Saturday");
  15. Stack stack = new Stack();
  16. stack.Push("Janurary");
  17. stack.Push("Feburary");
  18. stack.Push("March");
  19. stack.Push("April");
  20. stack.Push("May");
  21. stack.Push("June");
  22. stack.Push("July");
  23. stack.Push("August");
  24. stack.Push("September");
  25. stack.Push("October");
  26. stack.Push("November");
  27. stack.Push("December");
  28. Console.WriteLine("The elements in the arraylist are:");
  29. foreach (object obj in arr)
  30. {
  31. Console.WriteLine(obj);
  32. }
  33. arr.Insert(0, "********Names of the days*******");
  34. arr.Insert(8, "*********Names of the months**********");
  35. arr.InsertRange(9, stack);
  36. Console.WriteLine("The elements in the arraylist are after the insert operation:");
  37. Console.WriteLine();
  38. foreach (object obj in arr)
  39. {
  40. Console.WriteLine(obj);
  41. }
  42. arr.RemoveRange(9, 12);
  43. Console.WriteLine();
  44. Console.WriteLine("After apply the RemoveRange operation the elements are:");
  45. Console.WriteLine();
  46. foreach (object obj in arr)
  47. {
  48. Console.WriteLine(obj);
  49. }
  50. }
  51. }
  52. }

Here is the output.

arraylist_removerange.jpg

Reverse()

Reverses the order of the elements in the entire ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList();
  8. arr.Add(1);
  9. arr.Add(23);
  10. arr.Add(12);
  11. arr.Add(11);
  12. arr.Add(45);
  13. arr.Add(20);
  14. arr.Add(54);
  15. Console.WriteLine("The elements in the arraylist are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. arr.Reverse();
  21. Console.WriteLine("After apply reverse methods the elements are as:");
  22. foreach (object obj in arr)
  23. {
  24. Console.WriteLine(obj);
  25. }
  26. }
  27. }
  28. }

Here is the output.

arraylist_reverse.jpg

Sort()

Sorts the elements in the entire ArrayList.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList();
  8. arr.Add(1);
  9. arr.Add(23);
  10. arr.Add(12);
  11. arr.Add(11);
  12. arr.Add(45);
  13. arr.Add(20);
  14. arr.Add(54);
  15. Console.WriteLine("The elements in the arraylist are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. arr.Sort();
  21. Console.WriteLine("After apply sort methods the elements are as:");
  22. foreach (object obj in arr)
  23. {
  24. Console.WriteLine(obj);
  25. }
  26. }
  27. }
  28. }

Here is the output.

arraylist_sort.jpg

BinarySearch(object)

Searches the entire sorted ArrayList for an element using the default comparer and returns the zero-based index of the element.

For example:

  1. namespace ArrayList1
  2. {
  3. class Program
  4. {
  5. static void Main(string[] args)
  6. {
  7. ArrayList arr = new ArrayList();
  8. arr.Add(1);
  9. arr.Add(23);
  10. arr.Add(12);
  11. arr.Add(11);
  12. arr.Add(45);
  13. arr.Add(20);
  14. arr.Add(54);
  15. Console.WriteLine("The elements in the arraylist are:");
  16. foreach (object obj in arr)
  17. {
  18. Console.WriteLine(obj);
  19. }
  20. arr.Sort();
  21. Console.WriteLine("The sorted list is as:");
  22. foreach (object obj in arr)
  23. {
  24. Console.WriteLine(obj);
  25. }
  26. Console.WriteLine("The element 23 searched at:"+arr.BinarySearch(23));
  27. Console.WriteLine("The element 12 searched at:" + arr.BinarySearch(12));
  28. }
  29. }
  30. }

Here is the output.

arraylist_binarysearch.jpg

Summary

In this article, I've explained an ArrayList class and its methods and properties and how to use them in a C# application.

Next : C# SortedList