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Difference between "Last" and "LastOrDefault" in LINQ

In LINQ, Last and LastOrDefault are used to retrieve the last element from a sequence, such as a list or an array. They behave differently depending on whether there are elements in the sequence that match the specified condition.

1. Last

The Last method returns the last element that satisfies the given condition, and it assumes that such an element exists. If there is no matching element, it will throw an exception.

2. LastOrDefault

On the other hand, LastOrDefault also returns the last element that meets the condition, but it doesn't throw an exception if no matching element is found. Instead, it returns the default value for the type of elements in the sequence (e.g., null for reference types or the default value for value types like 0 for integers).

Let's illustrate this with a C# code example:


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

class Program
{
	static void Main()
	{
		List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };

		// Using Last
		int lastElement = numbers.Last(x => x % 2 == 0); // Finding the last even number
		Console.WriteLine("Last Element (Last): " + lastElement);

		// Using LastOrDefault
		int lastOrDefaultElement = numbers.LastOrDefault(x => x > 10); // No element > 10, returns default value (0)
		Console.WriteLine("Last Element (LastOrDefault): " + lastOrDefaultElement);

		// Using LastOrDefault with a default value
		int lastOrDefaultWithDefault = numbers.LastOrDefault(x => x > 10, -1); // Specifying a custom default value (-1)
		Console.WriteLine("Last Element (LastOrDefault with default): " + lastOrDefaultWithDefault);
	}
}

Now, let's look at the output:


Last Element (Last): 4
Last Element (LastOrDefault): 0
Last Element (LastOrDefault with default): -1

In this example, Last successfully finds the last even number (4), while LastOrDefault returns 0 as there is no element greater than 10 in the list. Additionally, we used LastOrDefault with a custom default value (-1), which returned -1 when no matching element was found.

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