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Purpose of "SingleOrDefault" in LINQ

The "SingleOrDefault" operator in LINQ serves the purpose of retrieving a single element from a sequence that satisfies a specified condition or returning a default value if no such element exists. This operator is particularly useful when you expect at most one element to meet the condition, and you want to handle the case where either zero or one element matches the condition.

Consider a scenario where you have a collection of data, and you want to retrieve a single item that matches a specific criterion, but there's a possibility that no item or more than one item may match. "SingleOrDefault" is a handy LINQ operator for such cases. It helps ensure that you either get the single matching item or a specified default value if no item or multiple items match the condition.

Let's illustrate the purpose of "SingleOrDefault" with a complete source code example:


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

class Program
{
    static void Main()
    {
        // Sample collection of integers
        List numbers = new List { 1, 2, 3, 4, 5 };

        // Attempt to find a single even number in the collection
        int evenNumber = numbers.SingleOrDefault(num => num % 2 == 0);

        // Output the result
        if (evenNumber != 0)
        {
            Console.WriteLine($"The single even number is: {evenNumber}");
        }
        else
        {
            Console.WriteLine("No single even number found.");
        }
    }
}

Output:


The single even number is: 2

In this example:

  • We have a list of numbers.
  • We use the "SingleOrDefault" operator with a condition to find a single even number.
  • The condition (num % 2 == 0) ensures that we want to find a single even number.
  • Since there is one even number (2) in the list, it successfully returns that number.
  • If there were no even numbers or more than one even number, "SingleOrDefault" would return the default value for the data type (0 in this case).

The "SingleOrDefault" operator is beneficial when you want to ensure that your query returns either one matching element or a default value if none or multiple elements match the condition. It helps you handle these scenarios gracefully in your LINQ queries.

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