LINQ | Element Operator | ElementAtOrDefault

The element operators are used to return a single, or a specific element from the sequence or collection. For example, in a school when we ask, who is the principal? Then there will be only one person that will be the principal of the school. So the number of students is a collection and the principal is the only result that comes from the collection.

The LINQ Standard Query Operator supports 8 types of element operators:

1. ElementAt
2. ElementAtOrDefault
3. First
4. FirstOrDefault
5. Last
6. LastOrDefault
7. Single
8. SingleOrDefault

ElementAtOrDefault Operator

The ElementAtOrDefault operator is used to return an element from the particular index from the given collection or sequence and it provides a default value if the index is out of range. It overcomes the ArgumentOutOfRangeException problem of the ElementAt operator.

• It does not support query syntax in C# and VB.Net languages.
• It support method syntax in both C# and VB.Net languages.
• It present in both the Queryable and Enumerable class.
• It does not throw an ArgumentOutOfRangeException when the index is out of range.
• The default value of the reference types and the nullable types is null.

Example 1:

// C# program to illustrate the use
// of ElementAtOrDefault operator
using System;
using System.Linq;

class GFG {

    static public void Main()
    {

        // Data source
        string[] sequence1 = {"Dog", "Cat", "Goat", "Parrot"};
        int[] sequence2 = {112, 44, 55, 66, 77, 777, 56};

        // Get the element at the given index
        // Using ElementAtOrDefault function
        var result1 = sequence1.ElementAtOrDefault(2);
        Console.WriteLine("Element at index 2 in sequence 1: {0}", result1);

        var result2 = sequence1.ElementAtOrDefault(4);
        Console.WriteLine("Element at index 4 in sequence 1: {0}", result2);

        var result3 = sequence1.ElementAtOrDefault(6);
        Console.WriteLine("Element at index 6 in sequence 1: {0}", result3);

        var result4 = sequence2.ElementAtOrDefault(2);
        Console.WriteLine("Element at index 2 in sequence 2: {0}", result4);

        var result5 = sequence2.ElementAtOrDefault(5);
        Console.WriteLine("Element at index 5 in sequence 2: {0}", result5);

        var result6 = sequence2.ElementAtOrDefault(8);
        Console.WriteLine("Element at index 8 in sequence 2: {0}", result6);
    }
}

Output:

Element at index 2 in sequence 1: Goat
Element at index 4 in sequence 1: 
Element at index 6 in sequence 1: 
Element at index 2 in sequence 2: 55
Element at index 5 in sequence 2: 777
Element at index 8 in sequence 2: 0

Example 2:

// C# program to find the
// ID of the employee
using System;
using System.Linq;
using System.Collections.Generic;

// Employee details
public class Employee {

    public int emp_id
    {
        get;
        set;
    }

    public string emp_name
    {
        get;
        set;
    }

    public string emp_gender
    {
        get;
        set;
    }

    public string emp_hire_date
    {
        get;
        set;
    }

    public int emp_salary
    {
        get;
        set;
    }
}

class GFG {

    // Main method
    static public void Main()
    {
        List<Employee> emp = new List<Employee>() {

            new Employee() {emp_id = 209, emp_name = "Anjita", emp_gender = "Female",
                                     emp_hire_date = "12/3/2017", emp_salary = 20000},

            new Employee() {emp_id = 210, emp_name = "Soniya", emp_gender = "Female",
                                    emp_hire_date = "22/4/2018", emp_salary = 30000},

            new Employee() {emp_id = 211, emp_name = "Rohit", emp_gender = "Male",
                                  emp_hire_date = "3/5/2016", emp_salary = 40000},

            new Employee() {emp_id = 212, emp_name = "Supriya", emp_gender = "Female",
                                      emp_hire_date = "4/8/2017", emp_salary = 40000},

            new Employee() {emp_id = 213, emp_name = "Anil", emp_gender = "Male",
                                emp_hire_date = "12/1/2016", emp_salary = 40000},

            new Employee() {emp_id = 214, emp_name = "Anju", emp_gender = "Female",
                                  emp_hire_date = "17/6/2015", emp_salary = 50000},
        };

        // Query to find the ID of
        // the employee at index 3
        // Using ElementAtOrDefault method
        var res = emp.Select(e => e.emp_id).ElementAtOrDefault(3);

        Console.WriteLine("Employee ID: {0}", res);
    }
}

Output:

Employee ID: 212