How To Find An Item In C# List

C# List Find. Check if an item is in the C# list or not. The Contains method checks if the specified item already exists in the C# List.

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");  
  16.   
  17.             // Contains - Check if an item is in the list    
  18.             if (AuthorList.Contains("Mahesh Chand"))  
  19.             {  
  20.                 Console.WriteLine("Author found!");  
  21.             }  
  22.   
  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