C# List<T> class provides methods and properties to create a list of objects (classes). The Contains method checks if the specified item is already exists in the List.
List is a generic class. You must import the following namespace before using the List<T> class.
  1. using System.Collections.Generic;
The following code snippet checks if an item is already exits.
  1. if (AuthorList.Contains("Mahesh Chand"))
  2. AuthorList.Remove("Mahesh Chand");
The IndexOf method returns the first index of an item if found in the List.
  1. int idx = AuthorList.IndexOf("Nipun Tomar");
The LastIndexOf method returns the last index of an item if found in the List.
  1. idx = AuthorList.LastIndexOf("Mahesh Chand");
The following code snippet shows how to use the Contains, the IndexOf and the LastIndexOf methods.
  1. using System;
  2. using System.Collections.Generic;
  3. namespace ConsoleApp1
  4. {
  5. class Program
  6. {
  7. static void Main(string[] args)
  8. {
  9. List<string> AuthorList = new List<string>();
  10. AuthorList.Add("Mahesh Chand");
  11. AuthorList.Add("Praveen Kumar");
  12. AuthorList.Add("Raj Kumar");
  13. AuthorList.Add("Nipun Tomar");
  14. AuthorList.Add("Mahesh Chand");
  15. AuthorList.Add("Dinesh Beniwal");
  17. // Contains - Check if an item is in the list
  18. if (AuthorList.Contains("Mahesh Chand"))
  19. {
  20. Console.WriteLine("Author found!");
  21. }
  23. // Find an item and replace it with new item
  24. int idx = AuthorList.IndexOf("Nipun Tomar");
  25. if (idx >= 0)
  26. {
  27. AuthorList[idx] = "New Author";
  28. }
  29. Console.WriteLine("\nIndexOf ");
  30. foreach (var author in AuthorList)
  31. {
  32. Console.WriteLine(author);
  33. }
  34. // Find Last index of
  35. idx = AuthorList.LastIndexOf("Mahesh Chand");
  36. if (idx >= 0)
  37. {
  38. AuthorList[idx] = "New Mahesh";
  39. }
  40. Console.WriteLine("\nLastIndexOf ");
  41. foreach (var author in AuthorList)
  42. {
  43. Console.WriteLine(author);
  44. }
  45. }
  46. }
  47. }
The output of above Listing looks like Figure 1.
C# List
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