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.

Next >> C# List Tutorial