LINQ | Element Operator | ElementAt

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

ElementAt Operator

The ElementAt operator is used to return an element from the particular index from the given collection or sequence. Here the specified index is zero-based index. Suppose an array contains 3 elements, i.e, 1, 2, 3 and we want to print the value at index 1, so we use an ElementAt method because it will return the element present at index 1, i.e, 2.

Important Points:

• 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.
• If the given index is out of range, then this method will throw an ArgumentOutOfRangeException.

Example 1:

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

class GFG {

    // Main Method
    static public void Main()
    {

        // Data source
        string[] sequence = {"Dog", "Cat", "Cow",
                               "Goat", "Parrot"};

        // Display the sequences
        Console.WriteLine("Sequence is: ");

        foreach(var s in sequence)
        {
            Console.WriteLine(s);
        }

        // Get element at index 3
        // Using ElementAt function
        var result = sequence.ElementAt(3);

        Console.WriteLine("Element is: {0}", result);
    }
}

Output:

Sequence is: 
Dog
Cat
Cow
Goat
Parrot
Element is: Goat

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 1
        // Using ElementAt method
        var res = emp.Select(e => e.emp_id).ElementAt(1);

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

Output:

Employee ID: 210