ElementAt() method in C#

The ElementAt() method in C# is a LINQ extension method that retrieves an element at a specified index from any collection that implements IEnumerable<T>. It provides a way to access elements by index in collections that don't have built-in indexing support.

Syntax

Following is the syntax for the ElementAt() method −

public static TSource ElementAt<TSource>(this IEnumerable<TSource> source, int index)

Parameters

• source − The IEnumerable<T> to return an element from.
• index − The zero-based index of the element to retrieve.

Return Value

Returns the element at the specified position in the source sequence. Throws ArgumentOutOfRangeException if the index is less than 0 or greater than or equal to the number of elements in the source.

Using ElementAt() with Arrays

Example

using System;
using System.Linq;

public class Demo {
   public static void Main() {
      string[] arr = { "One", "Two", "Three", "Four", "Five" };
      
      // Get element at index 0
      string firstElement = arr.ElementAt(0);
      Console.WriteLine("Element at index 0: " + firstElement);
      
      // Get element at index 3
      string fourthElement = arr.ElementAt(3);
      Console.WriteLine("Element at index 3: " + fourthElement);
   }
}

The output of the above code is −

Element at index 0: One
Element at index 3: Four

Using ElementAt() with Lists

Example

using System;
using System.Collections.Generic;
using System.Linq;

public class Demo {
   public static void Main() {
      List<int> numbers = new List<int> { 10, 20, 30, 40, 50 };
      
      // Get element at index 2
      int thirdElement = numbers.ElementAt(2);
      Console.WriteLine("Element at index 2: " + thirdElement);
      
      // Get last element using Count - 1
      int lastElement = numbers.ElementAt(numbers.Count - 1);
      Console.WriteLine("Last element: " + lastElement);
   }
}

The output of the above code is −

Element at index 2: 30
Last element: 50

ElementAt() vs ElementAtOrDefault()

The ElementAtOrDefault() method returns the default value for the type if the index is out of range, instead of throwing an exception −

Example

using System;
using System.Linq;

public class Demo {
   public static void Main() {
      string[] arr = { "Apple", "Banana", "Cherry" };
      
      // Valid index
      Console.WriteLine("ElementAt(1): " + arr.ElementAt(1));
      Console.WriteLine("ElementAtOrDefault(1): " + arr.ElementAtOrDefault(1));
      
      // Invalid index - ElementAtOrDefault returns null for reference types
      Console.WriteLine("ElementAtOrDefault(10): " + (arr.ElementAtOrDefault(10) ?? "null"));
      
      // ElementAt(10) would throw ArgumentOutOfRangeException
   }
}

The output of the above code is −

ElementAt(1): Banana
ElementAtOrDefault(1): Banana
ElementAtOrDefault(10): null

Common Use Cases

• LINQ Queries − Accessing elements by index in the result of a LINQ query.

• Collections without indexers − Accessing elements by index in collections like HashSet<T>.

• Method chaining − Using within LINQ method chains for more complex operations.

Conclusion

The ElementAt() method provides indexed access to any IEnumerable<T> collection. Use ElementAt() when you need to throw an exception for invalid indices, or ElementAtOrDefault() when you prefer to handle invalid indices gracefully with default values.