How To Find An Item In 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.

using System.Collections.Generic;

The following code snippet checks if an item is already exits.  

if (AuthorList.Contains("Mahesh Chand"))
    AuthorList.Remove("Mahesh Chand");

The IndexOf method returns the first index of an item if found in the List.

int idx = AuthorList.IndexOf("Nipun Tomar");

The LastIndexOf method returns the last index of an item if found in the List. 

idx = AuthorList.LastIndexOf("Mahesh Chand");

The following code snippet shows how to use the Contains, the IndexOf and the LastIndexOf methods. 

using System;
using System.Collections.Generic;
namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> AuthorList = new List<string>();
            AuthorList.Add("Mahesh Chand");
            AuthorList.Add("Praveen Kumar");
            AuthorList.Add("Raj Kumar");
            AuthorList.Add("Nipun Tomar");
            AuthorList.Add("Mahesh Chand");
            AuthorList.Add("Dinesh Beniwal");

            // Contains - Check if an item is in the list
            if (AuthorList.Contains("Mahesh Chand"))
            {
                Console.WriteLine("Author found!");
            }

            // Find an item and replace it with new item
            int idx = AuthorList.IndexOf("Nipun Tomar");
            if (idx >= 0)
            {
                AuthorList[idx] = "New Author";
            }
            Console.WriteLine("\nIndexOf ");
            foreach (var author in AuthorList)
            {
                Console.WriteLine(author);
            }
            // Find Last index of
            idx = AuthorList.LastIndexOf("Mahesh Chand");
            if (idx >= 0)
            {
                AuthorList[idx] = "New Mahesh";
            }
            Console.WriteLine("\nLastIndexOf ");
            foreach (var author in AuthorList)
            {
                Console.WriteLine(author);
            }
        }
    }
}

The output of above Listing looks like Figure 1.

 

 

 

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