LastOrDefault, Last

LastOrDefault is a helpful C# method—it finds the last element in a collection that matches a condition. In many cases Last() does the same thing.

With LastOrDefault() we get either the last matching element or the default value. Last meanwhile will throw an exception if no element exists.

LastOrDefault

This program shows the LastOrDefault method. The result is 3 for the first array. For the second array, which is empty, the result is 0 because the default int value is 0.

using System;
using System.Linq;

// Last or default.
int[] array1 = { 1, 2, 3 };
Console.WriteLine(array1.LastOrDefault());

// Last when there are no elements.
int[] array2 = { };
Console.WriteLine(array2.LastOrDefault());

// Last odd number.
Console.WriteLine(array1.LastOrDefault(element => element % 2 != 0));
3
0
3

Last

This program calls the Last extension method on an array. Last() is found in System.Linq and can be used on arrays, Lists, or anything that implements IEnumerable.

using System;
using System.Linq;

int[] values = { 1, 2, 3, 4, 5, 6 };
int last = values.Last();
int lastOdd = values.Last(element => element % 2 != 0);

Console.WriteLine(last);
Console.WriteLine(lastOdd);
6
5

Internals

How does the Last extension work? It determines if the collection type implements IList. The IList interface is implemented by arrays, Lists, and others.

Last and LastOrDefault access elements. Last has optimizations for Lists and arrays, but is also effective for other collections. LastOrDefault, unlike Last, throws no exceptions.