ElementAtOrDefault

The C# ElementAtOrDefault method accesses an element. It handles an out-of-range access without throwing an exception.

ElementAtOrDefault returns a default value if the index is not present. ElementAt meanwhile will throw an error on nonexistent indexes.

Example

In this program we create a 3-element array. The only valid indexes to access are 0, 1 and 2. We show how ElementAtOrDefault works on valid indexes, and also out-of-range indexes.

using System;
using System.Linq;

int[] array = { 4, 5, 6 };

// Call ElementAtOrDefault with various indexes.
int a = array.ElementAtOrDefault(0);
int b = array.ElementAtOrDefault(1);
int c = array.ElementAtOrDefault(-1);
int d = array.ElementAtOrDefault(1000);

Console.WriteLine(a);
Console.WriteLine(b);
Console.WriteLine(c);
Console.WriteLine(d);
4
5
0
0

ElementAt

This method gets an element at an index. In many IEnumerable types, you cannot directly index a certain element. ElementAt can help with these types.

using System;
using System.Linq;

// Input array.
string[] array = { "Dot", "Net", "Perls" };

// Test ElementAt for 0, 1, 2.
string a = array.ElementAt(0);
Console.WriteLine(a);
string b = array.ElementAt(1);
Console.WriteLine(b);
string c = array.ElementAt(2);
Console.WriteLine(c);

// This is out of range.
string d = array.ElementAt(3);
Dot
Net
Perls

Unhandled Exception: System.ArgumentOutOfRangeException:
    Index was out of range.

Index from end

With the "^" syntax, we can access an index from the end of a collection. So "^2" will get the second-to-last element.

using System;
using System.Linq;

var values = new char[] {'a', 'b', 'c', 'd'};
// Use "^" to index from the end.
var secondToLast = values.ElementAtOrDefault(^2);
Console.WriteLine(secondToLast);
c

An important note

Conceptually, ElementAtOrDefault can make a collection be infinite. It can make every possible index returning a valid value—the default value.

These methods can transform how we access collections. ElementAtOrDefault eliminates the need for bounds-checking, but it can create extra complexity when handling the default value.